A recent story that United had removed all instances of the word "God" (not simply Goddamn) from a historical movie reminded me just how much they censor the movies on planes.
Here they have an easy and simple way out. Everybody is on headsets, and they already offer different soundtracks in different languages by dialing the dial. So offer the censored and real soundtrack on two different audio channels. Parents can easily make sure the kids are on whatever soundtrack they have chosen for them, as the number glows on the armrest.