While the seedier side of Thailand's sex industry is on show in Patong (we'd be reluctant to bring our kids here, though many people do), the rest of Phuket is fairly G-rated.
Visits to Phuket Elephant Sanctuary, Phuket Aquarium, Soi Dog and the Phuket Gibbon Rehabilitation Project are terrific animal-themed activities for children. Adrenaline-addicted older kids can tackle kitesurfing in Rawai and Hat Nai Yang, or surf at Hat Kata Yai.
Phuket's most-advertised 'family-friendly' feature is Phuket Fantasea which, while popular, has significant animal-welfare concerns. We don't recommend it, or any of the many elephant rides that are offered on Phuket.