Any time a new cartoon movie is advertised on the TV, my almost 5 year old begs to go see it. We don't bring him to the movies very often, but occasionally as a treat. It is important to us that it is a movie we think he will enjoy and would be appropriate for him. Recently, a friend decided to bring her young daughter to see Rango and was upset to see how violent and in many ways inappropriate the movie was for her daughter. She assumed that with the PG rating and the cartoon cast it would contain the occasional adult focused jokes that would mean nothing to a young child and otherwise it would be a fine movie. I had been planning on seeing that same movie and now I'm thinking twice about it. It caused me to search out a way to check into the ratings for these movies, as a rating of G, PG, PG-13, etc. often means very little. Each family has their own values to uphold and something that offends my friend might not offend me. I have two sites I'd like to share with you to help you decide if a movie is appropriate for your kids or not.
The first is Parent Reviews. This site will tell you why the movie has been given its MPAA rating and goes into more detail about the movie. They give letter grades for Violence, Sexual Content, Language, Drugs/Alcohol, and the movie Overall. The offer a detailed review by an experienced reviewer, detail on the content of the movie, a place for reader comments and more.
The second is Kids in Mind. They offer a 1-10 rating system for sex & nudity, violence, and profanity then break down each of those ratings with scene details from the movie. This site is a bit more straight forward than the other, in that it does not give a review, just summaries of the questionable scenes for you to decide if it is appropriate or not.
Hope that helps!