Avatar is really good, and I suggest you buy the collector's edition (the one I own) because once you are done watching one of them, there are two others to look forward to. Now, onto content!
Battle Scenes and War: Most likely intense for younger viewers. The final battle sequence is between man and Na'vi, and is emotional, considering we see troopers of both sides get stabbed, shot, impaled and crushed by guns, spikes and falling objects. Parents need to know this entire battle is a bit graphic for children. Jake has many close encounters with shaman creatures, which may be intense and in many scenes, they chase him in an attempt to kill and eat him. The Na'vi's sacred tree is destroyed by human weapons, which some may find upsetting. Many positive characters are mortally wounded on-screen during the movie, which may be disturbing for the audience.
Sensuality: It contains one sex scene, extremely mild sex references and brief nudity. The Na'vi people are aliens, but they are humanoid creatures. They dress in a tribal way, and we see their butts (not fully covered by their tails) quite a bit. The men wear only loincloths, and the women wear loincloths and ornamental, stringy pendants as bras. Their breasts are partially seen through these accessories and from the sides at many points during the movie.Both Jake and Dr. Augustine are stripped nude (in human form) and wrapped in ivy for a special Na'vi ritual. Their backs are seen partially, but explicit nudity is hidden. Dr. Augustine tells Jake to stop playing with his queue.
Language: 11 uses of "s--t", 8 of "goddamn", 6 of "hell", 4 of "ass," 4 of "damn," 3 of "crap," 3 of "bitch," 2 of "Jesus", 2 uses of d--k (1 paired with god) and 1 use each of "for Christ's sake," "bastard," "oh my God," "my God," "oh God" and "son of a bitch." One each of "screwing", "screwed", "screw", "pissed off", "piss off", and "pissing", "balls.
Smoking: Grace smokes many times, and at one point asks for a cigarette with urgency. Jake pulls a cigarette out of her mouth and tells her not to smoke.