Not again. I reach for my watch. It's 5.04am. This is the third morning in succession we've been woken by howler monkeys. "Howl" isn't the half of it. The noise invades your consciousness like some distant wind and builds into a sustained, jet-engine roar until you fling off the sheets and sit up, cursing. Awake, you can hear the throaty rasp – like a vomiting Darth Vader. The volume is astonishing: this is reputedly the loudest voice on the planet yet it comes from an animal no larger than a cat.
Still, an early start is no bad thing. So far we've needed every minute of daylight to get through our breathless itinerary, and this morning at the Hacienda Guachipelín promises to be the most action-packed yet. We are, after all, the proud bearers of a "family adventure pass".
A short while later, strapped into harness and helmet and slightly regretting my immense breakfast, I find myself standing on a narrow platform overlooking a forested gorge. A steel cable arcs down through the trees to some invisible point on the other side. Now seems the last chance to voice my fears were it not for the fact that my nine-year-old daughter is already clipped on ahead of me. The last thing I see as she launches into the void is her grin.
This would feel more daunting, though, if we hadn't been zip-lining already a few days ago, on the slopes of Arenal volcano. Then, I found it terrifying, hurtling at unnatural speeds along 800m cables high above the canopy. Now I'm a little more confident. As I zigzag down from platform to platform I can relax enough to appreciate the gurgle of the river and the chorus of birdsong. There is even time to spot a troop of howler monkeys in the crown of a fig tree. By the time we swing off the final platform on a Tarzan rope – with the obligatory Johnny Weissmuller yodel – fun has definitely conquered fear.
But the adventure pass has not done with us yet. Next, we saddle up on the hacienda's patient horses and ride down to where the tumbling stream has become an impressive river. Waiting for us is a pile of outsize rubber rings. We're going tubing, it seems. Before we know it, we are pushing off into the current, abandoned to our fate like human Poohsticks.
Tubing turns out to be a disconcerting business: one minute we're drifting along admiring the scenery; next, the current is drawing us into another set of rapids and our world has exploded into spray and screaming.
The Hacienda Guachipelí* is the penultimate stop on our two-week Costa Rica family adventure tour. It lies on the slopes of the Rincó* de la Vieja volcano in the country's far north-west. Like the other volcanoes we've seen, this one belches sulphurous smoke. But the dry forest that cloaks the lower slopes is very different from the dripping humidity of a few days earlier.
"These volcanoes control our climate," our guide Daniel Monge had told us on day one, as he collected us from San José airport and drove east. He showed on our tourist map how Costa Rica's peaks line up to form a barrier down the spine of the country: the Cordillera Central. The eastern slopes, which fall away to the Caribbean, get most of the rainfall and are carpeted in lush tropical rainforest. The western Pacific slopes lie in the rain shadow, so their forests are more arid, with a dusty, thorny feel.
Our first stop was on neither slope, however, but in the misty highlands that divide them. We drove up a hairpin ascent to the 3,432m summit of Irazú, Costa Rica's highest active volcano. On a good day, apparently, you can see both coasts from here. We had no such luck but, as we tramped around the ashy wasteland, the swirling mist allowed glimpses into the flooded crater. In 1963 this crater spewed out enough ash to blacken the skies of San José for three years and send lethal mudslides sweeping through the outskirts of Daniel's hometown, Cartago.
By afternoon, clear skies gave us picture-book views of Turrialba, the next volcano on our route. An ominous plume of smoke rose from the summit and Guayabo Lodge, our stop for the night, was directly below. "Don't worry," said Daniel, "it's been doing that for three years." Thankfully, it has been a while since Costa Rica experienced anything like the eruption of Volcá* de Fuego, currently forcing thousands to flee their homes in Guatemala.
The highlands are coffee country. The next morning, we wound down through the plantations to the estate of Tayutic, where they still process local produce the traditional way – and visitors get to join in. Here, my daughter helped to sort good macadamia nuts from bad as they rattled down the chute, then attempted to crush dried coffee beans in a stone mill. Her face fell when she learned that to work as a picker she'd need to pluck at least 4,000 to fill one basket, and do it 20 times a day.
From coffee to sugar seemed a natural leap. We joined a group to watch as the estate's two oxen turned a huge mill wheel that crushed fresh cane to a sticky pulp. The children's eyes widened as first the fresh juice was boiled up into a slow-bubbling gloop of golden molasses, then the raw sugar was spread, chopped and sifted.
That evening, inspired, we cooked our own Costa Rican meal in the kitchen of Guayabo Lodge. Our hosts provided ingredients and instructions, and the chef kept a discreet distance as we chopped, mashed, drizzled and seasoned to produce our best shot at tortas de plátano (fried plantain and cheese fritters), ensalada de palmito (heart of palm salad), and the obligatory gallo pinto (rice and black beans). My daughter even baked a chocolate cake using pure local cacao. Our smugness at dinner that night was matched only by our gluttony.
Next up, the rainforest. A morning's winding drive led us down to Selva Verde lodge in the Caribbean lowlands. This was closer to what I'd been expecting from Costa Rica: hot and sweaty, with a backdrop of towering green. These forests are said to harbour the greatest biodiversity on the planet – and even the short path from reception to room was like an encyclopedia of tropical wildlife: leaf-cutter ants ferrying their trophies; a metre-long green iguana basking on its branch like a plastic dinosaur; and, best of all, a three-toed sloth peering down from an epiphyte-laden kapok tree, baby clinging to its coat.
The next afternoon, to up the wildlife quota, we headed down the road to Tirimbina Reserve, where a local ecologist Willy Aguilar led us across a hair-raising suspension bridge into the primary forest. Knowing the challenges of finding wildlife in this habitat, I had warned my daughter not to expect big beasts around every corner. But she was enthralled as Willy produced a succession of rainforest rabbits – or, at least, agoutis – from his ecological hat. One minute we were squatting to examine the diggings of an armadillo; the next, we were sniffing the pungent fruit of a kerosene tree, watching a toucan pluck figs with its preposterous bill or marvelling at the leaf architecture of tent-making bats.
Being with a guide also has certain practical advantages. "Avoid the handrails," advised Willy, as a marauding bullet ant (its sting explains the name) trundled past. "Don't touch," he cautioned, as we crouched to examine a thumbnail-sized strawberry poison dart frog in the leaf litter. "That's far enough," he warned, more sharply, as I parted the foliage to view an eyelash pit viper coiled on the leaf of a heliconia.
But you don't need a guide to find Costa Rica's wildlife. In fact, you don't even need to go looking for it. So exuberant is nature in this part of the world that wild creatures form an unavoidable backdrop to whatever else you might get up to. Thus, over a fresh pineapple juice at a café terrace, we had watched dazzling hummingbirds zip back and forth. And from our cable car on the slopes of Arenal I had spied a tamandua – a tree-climbing anteater – foraging for termites in the branches below.
Fun, adventure and wildlife came rolled into one on the Peñas Blancas river, below Arenal, when we floated downstream on inflatable rafts. This was boating with at least a semblance of control, and the water was calm enough for my daughter to take the paddle. Wildlife was unfazed by our quiet approach: green basilisks – nicknamed Jesus Cristo lizards for their ability to scamper across the water's surface – posed on roots; a pair of spectacled owls peered down from the tangle; and long-nosed bats roosting on a tree-trunk mimicked the S-shape of a serpent to deter any myopic predators.
There comes a point in any holiday, of course, when you must put down the cables, tubes, paddles, saddles, cameras and binoculars and simply crash out. Conveniently, Costa Rica comes with not only two idyllic tropical coastlines but also a geothermal spa at the foot of every volcano. We'd already tried the latter at the lush Arenal Hot Springs Resort, parboiling ourselves gently into a wrinkled stupor beneath the smoking summit. So, for our last two days – having wrung all possible adventure from our pass – we descend from Rincón de la Vieja to Playa Panama, on the Pacific.
Our hotel, Casa Conde del Mar, turns out to be perfect: the lush grounds, the huge pool, the lavish breakfast spread and the warm ocean just beyond. How better to wind down before the flight home? There's only one problem, and it comes at 5.03am on our final morning: a thunderous wake-up call courtesy of the planet's noisiest primate. I pull my pillow over my ears.
Mike Unwin travelled as a guest of Virgin Holidays Worldwide Journeys, which offers a 14-day "Costa Rica Family Adventure" tour for £2,695 per adult and £1,490 per child. It includes United Airlines flights to San José via Newark, mixed-board hotels, transfers and guided sightseeing. Departure dates for 2013 are 30 March, 3 August, 26 October and 21 December, in line with the school holidays (0844 225 1235; virginholidaysjourneys.co.uk).