At St Katharine's Dock, in the shadow of Tower Bridge, there was a surprisingly long queue for the River Bus to Greenwich. I was surprised not only that so many people wanted to travel on the Thames - which has never struck me as one of the world's loveliest waterways - but also that they all wanted to go to Greenwich. Having worked for a number of years in Woolwich, I have an unreasoning prejudice against South-east London, yet there we were, buzzing down-river, and suddenly it didn't seem so bad. 'Isn't this what you see on the opening of EastEnders?' observed my daughter Jessica, sketching in the air the famous squiggly bit of the Thames. We gazed at the river with new respect, even thrilling to the sight of the grotesque Canary Wharf building, the tallest in Britain.
'This used to be the busiest waterway in the world,' I explained, pointing out that at these warehouses and wharves - many of them now providing fancy apartments - dockers would unload goods from all over the British Empire. 'Hard to believe now,' said Jessica, looking out at riversides apparently devoid of human activity.
Greenwich Pier provided more tangible evidence of Britain's maritime heritage. Here can be seen the Cutty Sark, built for the China tea trade, which in 1871 sailed from Shanghai to London in 107 days (and in 1885 made the voyage from Sydney to England in 73 days). Nearby is Gipsy Moth IV in which, in 1967, aged 65, Sir Francis Chichester made his single- handed voyage around the world.
If our seafaring appetite had now been whetted, the National Maritime Museum was about to satisfy it with the heartiest banquet imaginable. It was difficult to know where to dig in first. In the Discovery and Seapower room we gazed on globes crafted before we knew of the existence of America. 'Imagine a world without America,' said Jessica. I must say it seemed an appealing notion. We learnt why Columbus sailed west to find a route to the Indies (the eastward route was blocked by the Arabs). And one misconception was scotched: nobody laughed at Christopher Columbus because he thought the world was round - hardly anybody in his day believed it was flat.
In the Nelson room we gazed with ghoulish delight at the uniform worn by the great man (actually rather a tiny chap) when he met his fate at Trafalgar. There's a small hole in the jacket, where a musket ball passed through, while his breeches and stockings are heavily bloodstained. What were Nelson's dying words? 'Something to do with somebody called Hardy,' said Jessica after due reflection.
Now that 'Ships and Seafarers' is a core subject on the national curriculum, your children will certainly have to learn all the whos, whys and whats of Nelson. Take them to the National Maritime Museum and you will give them a flying start.
There was more fun in the Pirates room. As well as a romp through fictional pirates (Robert Louis Stevenson's Treasure Island seems to be the key influence here), visitors discover something of the real world of piracy. Privateers, for example, were licensed by the king to attack and plunder ships from countries with which we were at war: the motto was 'no prey, no pay'. Clearly, the British have a robust tradition of bad behaviour abroad.
The Pirates exhibition runs until 5 September, with a special Pirates day on 28 August. Every day except Thursday and Friday there are half-hourly storytelling sessions, with a costumed pirate spinning a yarn (we were treated to a rollicking tale which proved too bloodthirsty for some tiny tots).
You could linger all day in the Maritime Museum. Sadly, we had no time to see the Barge House or the Arctic exhibition, complete with stuffed Emperor penguin brought back by Captain Scott in 1904. It was time to move on to the neighbouring Queen's House, built by Inigo Jones for Queen Anne, wife of James I of England. Anne was dead by the time it was finished in 1638, and it became the house of Charles I's French wife, Henrietta Maria. It has been handsomely restored, with much of the furniture and fittings newly made to original patterns. Worksheets are available to help children to interpret the house's rich history.
Children will need little encouragement to explore Greenwich's final great historical site, the Old Royal Observatory. Even more than dinosaurs, telescopes, stars and roomfuls of ticking clocks hold allure for them, and the magnificently revamped exhibition at the observatory tells the intriguing story of man's interest in the movement of heavenly bodies.
The observatory was founded by Charles II in 1675 for wholly pragmatic reasons. To establish herself firmly as the prime maritime power of the world - and to enable further discoveries of new lands - Britain needed pinpoint navigation for her sailors. In this area it led the world - it would be John Harrison's invention of the marine chronometer in the 18th century that would eventually allow sailors to plot their exact longitude position.
Through this combination of painstaking research and inspirational discovery, the Greenwich Meridian was established. Nobody, it seems, can visit the observatory without being photographed straddling the meridian line: one foot in the eastern hemisphere, the other in the western.
In the mid 19th century the development of the railways in Britain and America created the need for universal timekeeping (in the early days of rail travel, a voyager from London to Bristol, for example, had to set his watch back four minutes to Bristol time), and Greenwich Mean Time became the international standard.
After satisfying our hunger for matters nautical and temporal, we needed refuelling of a more practical nature. We repaired to the excellent Bosun's Whistle Cafe in the National Maritime Museum, where I expected to be offered the usual institutional eatery hardtack. In fact the victuals were excellent and surprisingly good value.
Jessica tucked into a generous portion of fish and chips appropriate to a maritime ambience. 'Greenwich Meal Time', she remarked between mouthfuls.
Further information: A Passport ticket for Historic Maritime Greenwich (081- 858 4422) which allows admission to the National Maritime Museum (and Pirates exhibition), the Old Royal Observatory, the Queen's House and Cutty Sark, costs pounds 7.45 (concessions pounds 5.45); a family ticket (admitting two adults and up to five children) costs pounds 14.50; children under seven free. Opening hours are 10am to 6pm Monday to Saturday (Sunday 12 to 6pm). You can reach Greenwich either by River Bus or by the Docklands Light Railway to Island Gardens, then under the foot tunnel to Greenwich Pier.