This moving was amazing. From the graphics to the plotline, it was simply incredible.
There is one major kissing scene which may be innapropriate for children under the age of 10. It's not too much of a concern, being that it's really only about 5 minutes of the entire 3-hour-long movie.
Also, the language may also be a little problem for those under the age of 9. I wouldn't worry about the smoking or anything. I hardly picked up on it, and I'm sure no child would want to smoke just because one evil character in a movie did so.
One of the best parts about the movie, however, is that it satisfies a huge range of ages. Kids ten and under will love the dragon-like creatures and adventures the main character has as an avatar, while adults and teens will enjoy the movie for all of the other factors it has to share. This was, no doubt, one of the best movies of the 21st century.