Didn’t the New Mickey Mouse club kids do really well as adults? Britney Spears being the exception. But she’s rebounded and her career is going good again.
Justin Timberlake, Christina Aguilera, Ryan Gosling all have done well. Tony Lucca was on the Voice last year.
Jodie Foster
Jerry Mathers and Ken Osmond also did well after LITBeaver.
Van Dyke Parks is another success story. (Yes, he was a Hollywood film and TV child actor in the 50’s.)
Jackie Cooper. He was “Jackie” in the old Our Gang series, and played various roles in movies, including Jim Hawkins in the original 1934 Treasure Island. You all probably know him better as Perry White in the Superman movies.
The entire “The Outsiders” cast that included among others Tom Cruise and Patrick Swayze. They were adolescent rather than kids, admittedly. But teen actors/actresses are just as vulnerable. Another group I can think of is the Brat Pack of which John Cryer and Rober Downey Jr. were part.
How 'bout Brooke Shields?
My most favorite in the child actor area is Mary-Kate & Ashley who are now successful fashion designers. 
God bless you and them always!!!
Holly (a day one fan of them)
Kurt Russell. Worked steadily in small parts through the 50’s & 60’s, landed a contract with Disney and then joined up with John Carpenter and the rest is history.
Mark Lester, the anti-thesis of co-star Jack Wild.
Petula Clark, mostly remembered nowadays for her signature hit Downtown, but began her career at age 9. She has one of the most remarkable ‘debut’ stories ever - during WWII, she and her father were audience members attending a live radio broadcast to the troops abroad when a Blitzkrieg air-raid occurred. The studio was below ground, and so the audience remained there for an extended period. To keep everyone’s morale up, the announcer asked if anyone would like a chance to sing on the radio. Up stepped Pet Clark, and she was an immediate sensation. By the time she was 17, she had performed on radio, onstage, TV and in movies and sold millions of records.
As an adult, in her 60s heyday, she was an AM radio staple and for a time was the biggest-selling recording act in the entire world, beating out even the contemporary Beatles.
Alyssa Milano (Who’s The Boss–>Charmed) has done okay–still gets steady work on TV and video.
Sean Astin (The Goonies–>LOTR) He gets a lot of work.
Jason Bateman (Little House on the Prairie–>Arrested Development) He’s been in several movies lately.
Henry Thomas (E.T. --> small parts in lots of movies) Probably my favorite because I’m the same age and I grew up watching him in E.T. and Cloak & Dagger over and over again.
Jerry O’Connell went from “the fat kid in Stand By Me” to “the guy nailing Rebecca Romijn”.
And spent his teens as the lead for roughly seventy episodes of MY SECRET IDENTITY before spending his twenties starring in roughly seventy episodes of SLIDERS before spending his thirties doing supporting work in yet more episodes than either of those on CROSSING JORDAN – and, sure, starring in a whole bunch of failed shows to boot, but, hey, the point is that (a) he gets steady work on the small screen in between getting plenty of movie roles, and (b) again, Romijn.
No trainwrecks I can see; just an upcoming film with Patrick Wilson and Liv Tyler.
Leonardo DiCaprio isn’t doing too poorly.
Not exactly a “star,” but Robbie Rist (Cousin Oliver on “The Brady Bunch” and the second Dr. Zee on the original “Battlestar Galactica” became a musician and is still doing some acting.
We should add Annette Funicello. She was brought down by disease, not from “crashing and burning.”
And Mickey Rooney, who survived, even though his career diminished.
Angela Cartwright.
Drew Barrymore.
Tatum O’Neil.
We’re including people who did crash and burn, then later straightened out, right?
This one came to mind because I’d been watching Close Encounters of the Third Kind the other day, and looked him up out of curiosity:
Cary Guffey, who played the little boy, Barry, in CE3K when he was about 4, had a modest career as a child actor, but stopped acting by the mid 1980s. According to his entry on IMDB, he’s married with a couple of kids, got his MBA, and works as a financial planner.
Robert Downey Jr. has his act together now, but he spent many years being the very definition of “train wreck”.
And, some definitions of that group include Charlie Sheen, who makes Downey look like a choirboy.
You should probably include his brother, Clint, though it doesn’t appear he would have an acting career as an adult if his brother didn’t cast him in most, if not all, of his films.
Dean Stockwell. Started acting when he was nine and still is, in his seventies.
Christina Ricci
Anthony Michael Hall
Melissa Joan Hart
Hilary Duff