Genuinely good for children who like animals and boats, with one hard rule that shapes everything: the sea here is not for swimming.
Sea Turtle Conservancy visitor centre
A small museum on turtle biology, migration and the station's research going back to the 1950s, open 08:00–12:00 and 13:00–17:00 daily at US$2.50 per person, 200 m north of the school. Short enough to hold young attention and it explains everything you will see afterwards.
Ask for a small boat and a morning slot
Children see far more from a small boat or a paddled canoe than from a big motor launch — you get closer to the caimans, herons and basilisks and it is quieter. Specify a small group and an early departure when you book with a village guide.
Caño Palma Biological Station
A working research station up the canal at San Francisco, run by the Canadian non-profit COTERC, which hosts volunteers, interns and university field courses. Visits are arranged in advance rather than by turning up, and it suits teenagers with an interest in biology.
Turtle walks have rules, and often an age limit
Nesting tours go out at night in fixed groups with a licensed guide, with no torches, cameras or phones, and operators commonly set a minimum age. Ask about the age rule before you promise it to a child, and expect a lot of standing quietly in the dark.
Do not swim in the sea
The beach at Tortuguero has strong currents and is not safe to swim from, and the canals have caimans. Swimming here means a lodge pool, and only some lodges have one — worth factoring into where you book.