Leonardo di Caprio, Jodie Foster, Natalie Portman, Ryan Gosling, Jason Bateman, Neil Patrick Harris, and Anna Paquin are, on top of my head, child actors who've had very successful careers as adults.
Interesting enough, now working in LA in this business for three years, I have had some conversations with long time talent wranglers and studio teachers about working with young talent, and the one thing that they always mention is they hate seeing parents pushing them into doing it as if they never had a choice, and then they grow up hating their life because they never had a childhood.