My kid absolutely loved Avatar: The Last Airbender. After every episode, she would give me lengthy disquisitions on what had happened, her favorite characters, why what was going on was important, why she thought this person had done this thing, why it mattered. I saw only random episodes, but I read enough critical work on the show to be deeply impressed. When I heard a movie was being made, I was pleased -- as much for the kid as because we'd have a show we could see together.
However: Here's why you should NOT go see the movie.