San Teodoro is perfect for families, mine were all young uns.
The nearest beach is La Cinta, that's the one I posted the pic of. Within 10min drive are some of the best beaches I've ever used. Some in wildlife reserves so they charge a few € to park but you can come and go all day with the same ticket. Because they are on reserves there is no building by the beaches, in fact, the building regs mean they can't build too close to the beach anyway.
The whole island is great for a relaxed beach holiday if I'm honest.
It's typically Italian and can be very busy in August but my eldest is nagging us to go back.