I read the books to my boys, ages 3, 5 and 7. I don't like the moron and idiot-type references, but was disappointed that in the movie Greg uses the word "Crap." It was really not neccessary. Ditto with the boobalicious motorcycle magazine cover. Don't recall that being in the book, and really, really not necessary for a movie targeting little boys (let's try to keep them little as long as possible, kay?)
Other than that, my oldest was very upset that the movie "left out a lot of stuff" but it was a good lesson for him to learn that the book is ALWAYS better than movie. I really hope there will be more Wimpy Kid movies, just without the sex and border-line profanity.