With children, three criteria matter more than how beautiful a place is. First, a lagoon that stays knee-deep over a long distance, so you can supervise without stress. Second, shade close enough to the water's edge to keep the children in view from the mat. Third, toilets, which radically change a full day out. Three spots tick all three boxes: Mont Choisy in the north, Palmar in the east and Blue Bay in the south-east.
Mont Choisy is probably the outright best choice: the casuarina forest comes down to the sand, the lagoon is shallow for dozens of metres, and there are tables, toilets and parking. The downside is the Sunday crowd — arrive before 9am or come on a weekday. Palmar offers the same layout far more quietly, with the easterly wind as the trade-off: mornings only.
Blue Bay adds an unbeatable argument for 7- to 12-year-olds: mask and snorkel are actually useful right from the shore, in a marine park where fish are visible a few metres out. It's often the first time a child sees a parrotfish, and it marks a whole holiday. Bring oxybenzone-free sunscreen, as the site is protected.
For a change from sand, Bras d'Eau National Park works surprisingly well with children: permanent shade, tables, short flat trails and a real chance of seeing birds. It's also the best plan on days that are too hot or too windy. Alexandra Falls, further south, offers the same coolness with a spectacular view but no swimming — best kept for children who already walk well.
To avoid with little ones, despite their beauty: Gris Gris and Le Souffleur, where swimming is forbidden and genuinely dangerous, Tamarin where the swell comes right into the bay, and all the basalt coasts such as Roches Noires or Albion, where sharp rocks and the absence of a reef barrier make supervision exhausting.
