Honestly this is not a children's resort: it is a pilgrimage town at 3,815m where the lake is too cold to swim and the main sights are a church and a long boat ride — but small children do well on the beach and at the blessings.
Pedal boats on the beach
Brightly painted swan-shaped pedalos hired by the half hour on the town beach at the bottom of Avenida 6 de Agosto. Cheap, slow, and reliably the highlight of the trip for anyone under ten.
The blessing of the vehicles
Cars, minibuses and lorries line up in front of the Basilica covered in flowers and paper garlands to be blessed with holy water and beer, mostly at weekends and heaviest on feast days. Free to watch and over in about ten minutes.
The town beach
A shallow sandy strip along the bay with stalls, moored boats and room to dig. The lake stays cold all year, so this is paddling and picnic territory rather than swimming, and the altitude sun burns fast — hats and sunscreen.
A day boat to Isla del Sol
The standard outing: a slow crossing to Yumani at the southern end, a steep climb up the Inca steps from the jetty, then a walk along the ridge. Allow a whole day, and be realistic about whether your children will manage a long stone staircase at altitude.
Take the first day off
Children feel altitude as much as adults do — headache, broken sleep, no appetite. Come up from La Paz rather than straight from the coast, do nothing at all on arrival day, drink far more water than feels sensible, and note that the pharmacies on 6 de Agosto sell soroche tablets.