Carol Sarler: There's far more to happy families than two parents, two children and a jam sandwich

If you have no plans for tomorrow's bank holiday afternoon, do not panic. There are people out there with funky plans so firmly in place that all you need are sufficient sandwiches and a hefty chunk of goodwill to earn your participation in what is expected to be the Guinness record-breaking World's Largest Picnic. Under the slogan "Bringing Families Together", this co-ordinated event, at locations dotted around Britain's green bits, urges you to "stand and be counted" and take pride as you kick off the inaugural National Family Week.

The week includes the chance to compete for the Favourite Family Recipe, to be judged by Antony Worrall Thompson – this could be something handed down through generations, they suggest, or perhaps the first birthday cake you ever made – as well as the chance to congratulate the eventual winners among the finalists already chosen for Family of the Year. The lucky things will have £5,000 of Sainsbury's shopping and even get to go to Butlins for free.

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These are but two among many sponsors of National Family Week; the world of commerce, from Bupa to Pizza Hut, has jumped aboard. Every one of the main political parties, plus Boris Johnson, is endorsing it – well, of course they are; imagine the "message" that would be deduced from a refusal – and celebrities decorate the website with their enthusiasm, from Esther Rantzen and Terry Wogan to Joe Swash. (He won I'm a Celebrity..., people; do keep up.) The intention, clearly, is to celebrate the noble institution of the family and perhaps, they might even claim, to invigorate it. In which case, what's not to like? And yet, that said, an hour spent playing with the devil in the detail left me distinctly uneasy.

It's not just the thought of the picnic itself – jam has its place and its place is behind closed doors – but the squeamishness goes deeper. A close look makes it evident what the sponsors really mean, behind all their gaiety, when they applaud the "family".

Among the celebrities lining up to give their blessing, the closest to a black or brown face is Richard Madeley's suntan. By the same token, good money says that whatever the winning Favourite Family Recipe turns out to be, it won't contain a heck of a lot of cardamom. And if you've yet to get the gist, the Family of the Year will provide it: each of the finalists has triumphed over adversity or done splendidly good works or, more usually, both. Yet it is starkly noticeable that, in each case, there are two parents and sensibly spaced children who all share a surname. Has there never been a single mother who, together with her children, has fought the odds and won? A gay couple that has rescued an adopted child from despair – or worse? Are these not "families" too? Apparently not, at least not during National Family Week.

In short, the prevailing mood of the fun and games is a rather grisly cocktail of desperation and propaganda; the template family is not only a hark back to a real or imagined way it used to be, but also a determined application for its resurrection.

As irritants go, let me count the ways. First, obviously, for the exclusion of the many in favour of the elevation of the few: no matter how the organisers wish to present it, the "typical" Kellogg's Corn Flakes family, where Papa goes out to work while Mama stays home to care for their pair of chicks, actually numbers approximately 7 per cent of all families. As in the US, there are now more British women unmarried than married. And, although at the moment this includes widows and widowers and divorcees, the Office for National Statistics predicts that by 2031, barely a generation away, husbands and wives will be outnumbered by people who have never married.

It is an impertinence to suggest this change has been propelled by other than personal choice. Factor in anything you like – female earning power, controlled conception, social libertarianism, decline of church authority – but people learn, they make choices, and some of us are fed up to the back teeth with being chided for doing so. My own father was an upstanding officer in a more buttoned-up time; however, he watched all three of his children shack up with partners to whom they weren't married. After my mother, his wife, died he not only did the same but also admitted that seeing it work for us had directly influenced him to follow suit.

He probably thought that the nuclear family in which he had once believed but then abandoned had, as its advocates still like to pretend, gone on for ever. In fact, we know, it is not only an artificial construct but also a recent one, scarcely 200 years old, a product of an industrial revolution that required small, mobile units as a workforce. As such, requirements have altered, so have we. But it is infuriating to be told, as we so frequently are, that the decline of the nuclear family is commensurate with the decline of "family" itself.

Pause. Stick head out of front door. Do window count. There are 18 dwellings on the other side of the road; about another 30 on my side. There is not one, single Kellogg's Corn Flakes family unit between us. But families? We number plenty.

Indeed, from where I sit, I am proud that the family is alive and well; further, delighted that blood still binds, even (especially?) when we have the freedom to walk away and even when, without that blood, we might have no bind at all. Last week, the writer Peter Hitchens was asked – yet again, poor chap – about the famously fraught relationship between him and his brother Christopher. "We're different people," he said. "If we weren't brothers, we wouldn't know each other." But given that they are brothers? "I had dinner at his place three weeks ago." That's family.

Similarly, I remember a night in the late Sixties when I'd smuggled my teenage self out of the house, then back into the bedroom shared with my sister. I'd been to score the makings of a spliff; she was sitting up in bed reading Billy Graham. With the belligerent confidence of the righteous, she demanded to know: "Don't you want Jesus Christ to save your soul?" I tell you, "different people" doesn't begin to cover it. And yet, last month, just as the the brothers Hitchens were breaking bread, she and I were away on holiday, bickering amicably about the propagation of morning glory. That's family.

My sister gave up on my soul. And she settled in the West Country where she now lives, with no husband but two adult sons, instead. In London I share a house with an adult daughter who – courtesy of a lovely but not live-in boyfriend – is soon to swell the household with another, due in early December. I even went to the scan on Thursday. That's family.

One friend is commuting between London and Wales, the better to nurse her divorced sister through chemotherapy; another, a man, is helping to raise the child of a sibling who, sadly, lost that same battle. That's family.

"Broken", they call us. Or, in the papers that favour syllables, "dysfunctional". They wheel out teenage pregnancies; knife crimes; binge drinking; they blame us for the lot of it. Still, their bleak half-empty is my shimmering half-full. Given the astonishing rapidity of the change in social order, not to mention the absence of political or other support, I think most of us have done fantastically well with our bonds and care and, yes, our love.

There is a great deal to celebrate about the contemporary British family, in all its multiple guises. But when celebration is purposely restricted to a confection of Mr & Mrs and their do-gooding little 'uns, it's a picnic too far for me. Let them suck on their lolly sticks. But let them also know this: though their rigidity might not be dead yet, it belongs to a dying breed.