Call it an exercise in contrasts. At the summit of Mont Saint-Michel, the bronze statue of the archangel is glinting in the midday sun, sword raised and wings outspread. At the foot of Mont Saint-Michel, a small jam-smeared boy is wriggling through a tiny window in the fortress wall and idly breaking into the courtyard of a gendarmerie. The archangel is the protector of the mount. The boy is my son.

Four of us – me, my wife, our four-year-old daughter Bethan and seven-year-old apprentice cat burglar, Joe – have come to western Normandy to join 15 other British families on an all-ages adventure break. This group day trip is a mere bit-player in the week’s itinerary. The holiday is primarily based 45 minutes inland, at an old countryside chateau near Les Chambres on the Manche coast, near Brittany. It’s a wholesome setting in which rabbits hop, peacocks preen and mobs of croissant-fuelled children tear around, brandishing makeshift lightsabers.

“Bonjour,” grins the chief animatrice, or activity hostess, welcoming us when we first arrive. “I am Lilie, and this week I will be in charge of your ’appiness.” She points us towards a trestle table lined with glasses of champagne and mint lemonade. There are already kids scampering across the garden in front of the chateau. The four-year-old is clingy; the seven-year-old vanishes within seconds.

Having never previously opted for a holiday of organised fun, we are, in truth, wary about what’s to come. Our free-range instincts are having to be repressed. The programme contains daily tailored activities for different ages, adults included – everything from treasure hunts and raft-building to bread-making and wine-tasting. The kids are to be swept off and entertained by holiday staff, while we’ll be led elsewhere and busied with grown-up pastimes – or that’s the idea.

But what if the kids don’t want to get stuck in? What if the timings are too rigid? What if it tips it down and we’re commandeered against our will to go clay-pigeon shooting in the woods?

We establish a few guidelines. Firstly, it turns out everything’s optional. If we want to spend our time sitting in the sun, counting daisies, fine. Secondly, the chateau might not have the moat and portcullis the seven-year-old was hoping for but the grounds are big and bucolic, with hulking beech trees and lawns that seem to slope off interminably. There’s a lake, a forest and a fridge with beer in it. Exhale.

Thirdly, and vitally, it soon transpires that doing fun things is fun. On the first day, Bethan is petting guinea pigs at the mini-farm, Joe is on the climbing wall, my wife’s on a bike ride and I’m on the lake getting over-competitive in a canoe. The other parents turn out to be a friendly bunch. When the family reconvenes at the communal dining hall, flinching only slightly at being instructed where to sit, all four of us seem happy.

Most days follow the same pattern: breakfast, morning activities, lunch, afternoon activities – pause for breath – family activities, dinner and, finally, evening entertainment. We still seem to spend a large part of the day with the kids. Perhaps unsurprisingly, we all sleep soundly.

If the itinerary appears regimented on paper, in reality it’s much looser, thanks largely to the staff, a motley French-English collective with a knack for knowing when to be sensible (during potentially hazardous activities) and when to be silly (at all other times). Lilie who, at first, had appeared quite sane, reveals herself to be a whirligig of water bombs, crazed songs and ill-fitting superhero costumes. The kids see her as a sort of Frère Jacques-chanting deity.

There’s a range of accommodation, including yurts and rooms in the chateau itself, but we’re staying in one of two new forest treehouses deep in the grounds, 10 minutes’ walk from the main building. The setting is green and quiet, and the treehouse serves as our daily sanctuary – a pine-clad hidey-hole where the only sound is that of falling fir cones. It’s on canopy-level stilts, rather than being perched among actual boughs, and has a large balcony and comfortable beds. Leaving each morning is difficult.

On the basis that happy kids equal happy parents, the week is a roaring success, even if we don’t always quite understand what each other is doing. Joe starts raving about something called aeroball, which seems to be a cross between trampolining and basketball. My wife and I fall for a game involving wooden sticks named mölkky. And Bethan thinks my first foray into fencing means I’ll be throwing swords over a fence, when, in fact, I’ll be pitched into armed combat with a veterinary nurse from Leamington Spa.

The obvious reservation about a holiday like this, of course, is that you’re coming to Normandy but surrounding yourself with other Brits and seeing precious little of the region. True enough, although, on the whole, the experience still feels French. As well as the aforementioned day trip to Mont Saint-Michel (the gendarmerie break-in, incidentally, results in release without questioning), there’s an outing to a goat farm, optional language lessons and due prominence given to the holy trinity of cider, cheese and pétanque. The week’s menu is largely Gallic, too. It includes a seafood banquet, proper quiche lorraine and even a platter of frogs’ legs and snails, which engender predictable howls of horror/wonder from the kids.

One afternoon there’s an assault-course challenge in the woods, which results in everyone getting coated head to toe in mud. Joe is in heaven. He and I trudge back to the treehouse, still dripping in sludge. “Daddy,” he says, placing his filthy hand in mine, “I wish we always lived here.” He may not be given to rational ideas, but he knows a good week when he’s had one.

Way to go

The seven-night Normandy Chateau Adventure was provided by Family Adventure Holidays, which is available from 22 July-2 September 2017. From £440 adult, £395 child aged 6-15, £155 per child aged 2-5 (under-twos free), including all activities, meals and drinks. Ferry provided by aferry.co.uk; summer fares from Portsmouth to Cherbourg from around £350 return for a car and family of four with Brittany Ferries