I always wonder why film makers find it necessary to include any remotely sexual content in movies marketed to young children. Although it may fly right over the heads of younger kids or older, desensitized children -- there are scenes involving the older sister and her boyfriend (who, it is revealed in the movie, has lied about his age in order to date a younger girl) which seem a bit naughty. There are public displays of affection, a scene near a pool where the girl sits in a revealing bikini and inferences that the boyfriend has lied about his car breaking down in order to spend the night in the same house with the girl(some might even infer that he wishes to sleep with her.) As is usually the case, the adults are portrayed as clueless and unresponsive to the concerns of their younger children.
As for the alien activity, I didn't find it at all scary and there is one friendly alien who is downright adorable. There is some slapstick-type violence and a few explosions. Overall, the movie is entertaining for older children and adults. My 12-year-old son enjoyed it.