Who is one of the most -if not THE -most sucessful ex-child actor,who,besides his roles in The Andy,Griffith Show,and Happy Days,and directing,made a lot of guest appearances on 1960's TV shows and movies(including the 1980 NBC made for TV movies"Act of Love"and "Bitter Harvest"after he left "Happy Days",and returned to do 2 other episodes of "Happy Days"(part one was very good.part 2 was only so-so,except for the great ending,and the last show of the series),and 1986's reunion of "The Andy Griffith Show",the 1986 TV-movie "Return to Mayberry",as an older and happily married Opie.Anyway,name OTHER ex-child TV actors who had a successful career AFTER the show they were on ended.and DID NOT end badly.

Jodie Foster was in the TV version of Paper Moon and guest starred in quite a few series in the late 60's -mid 70's before hitting it big in the movies. Nancy Mckeon starred in a lot of TV movies and in The Division after The Facts of Life ended.

Sarah and Melissa Gilbert did pretty well for themselves.

Mickey Rooney.He actually started as a child actor,and became one of the most successful(and one of the best) young adult and then adult actors ever,both in television and movies.Dean Stockwell is another,he became a fantastic and very successful adult actor.Kurt Russell,not in the same league as the other two did ok also.

A sidenote:About Ron Howard.There is no doubt he was a good child and adult actor.However didn't he get way to much work especially as a child actor.It seemed whenever they needed a child or teen actor often Ron Howard got the part guest starring in so many shows and appearing in alot of movies.There were alot of other talented child,teen etc actors of his era that were just as good or even better than him.

The Travels of Jamie McPheeters (1963-1964) with Kurt Russell. He has done very well in his career, which is still going strong.
Veronica Cartwright (Daniel Boone) is still acting also. She was in her first movie in 1958...uncredited.

Who is one of the most -if not THE -most sucessful ex-child actor,who,besides his roles in The Andy,Griffith Show,and Happy Days,and directing,made a lot of guest appearances on 1960's TV shows and movies(including the 1980 NBC made for TV movies"Act of Love"and "Bitter Harvest"after he left "Happy Days",and returned to do 2 other episodes of "Happy Days"(part one was very good.part 2 was only so-so,except for the great ending,and the last show of the series),and 1986's reunion of "The Andy Griffith Show",the 1986 TV-movie "Return to Mayberry",as an older and happily married Opie.Anyway,name OTHER ex-child TV actors who had a successful career AFTER the show they were on ended.and DID NOT end badly.
Ron Howard also played Henry Fondas son in the short lived series "THE SMITH FAMILY" on ABC in the 70s.

And Ron Howard Brother Clint Howard aka Silent Leon on Andy Griffith show also play on the My Dog Skip Movie

Clint Howard also had a small role as a mission controller in Rons movie "APOLLO 13".

I think the only other ones I can think of are probably Jason Bateman and Michael J. Fox, especially the former.

Jason Bateman was not only working on 3 80s NBC sitcoms but on one of those sitcoms, he became one of the youngest people to ever direct a TV show at the age of 18. He also had a moderately successful sitcom in the mid 2000s and starred on a few number of films as well.

As fr MJF, he had two successful sitcoms and was working on a franchise movie during the peak of Family Ties.

Ditto for Melissa Joan Hart.

Kristy McNichol did well as a child actress. She did Apple's Way, Family, guest starred on episodic tv shows like Love Boat and was in movies. As an adult she was in Empty Nest.

meloria hardin now best known as jan levinson on the office has been working almost nonstop in tv and movies since 1977 so she has very quietly become a child actor who has done pretty well for herself with a minimum of fuss

After The Facts of Life:

Kim Fields is doing well. She was on the hit Living Single for 5 years and she directed some episodes of that as well as directing some episodes of Tiana, some episodes of Kenan & Kel, some Tyler Perry sitcoms, etc.....

She is now on Dancing With The Stars and she just wrapped up a season of The Real Housewives of Atlanta.

Drew Barrymore, Jason Bateman, Danica McKellar, Joseph Gordon-Levitt, Mayim Bialik, Alyssa Milano, Elizabeth Taylor, Neil Patrick Harris