I think Avatar is appropriate for a seven year old, and I think that a boy would especially love it. He might be bored during the first parts of it that actually explain what's going on, but as the movie develops and there are more action scenes, I'm sure he'll be juiced about it. There's barely any sexuality, which I doubt he'd pick up on anyways, and the violence isn't gory. This is definitely not the type of movie that will leave a child sleeping in his parents' bed for the next month nor is it one that will have a negative influence on him. If anything, he might pick up a lesson from the storyline.