No matter what the age of your children, you do not want to be caught off-guard while watching a family movie. Every family has its own value system that each parent tries to instill into their children. No parent likes to have their value system violated, especially by a movie that they initiate.
There are a few websites that do an excellent job of screening movies for families then writing up the details for parents to make informed decisions.
Plugged In Online does a great job of going through the content of a movie and giving specific details divided into content areas. This allows parents to focus in on specific areas that match their value system.
Kids In Mind is an excellent website that has a fantastic catalog of movies rated using their three scale system.
The Dove Foundation has been an advocate of family-friendly movies for many years. Not only do they have an extensive library of movie reviews, but they also are active in working with the movie industry to produce movies that are more friendly to the family.
Check out Family Capers' activity for Family Movie Night for some fun ideas!