XBMC supports user profiles. I have a Kids, General, Mature profile. The kids can watch whatever is in the Kids profile, no pin set, and so can any carers. The General is Kids+ the rest of the movies and TV shows which it is okay for the content to be watched while we are nearby to supervise/explain. General is what I would generally have loaded by default. Mature is any video/TV that I don't want the kids to watch yet - pin protected. So far it works really well. Just have three directories per set that hold the content as you decide they fit the scheme. Kids only reads from TV - Kids and Movie - Kids, General reads Kids + General, Mature reads Kids + General + Mature etc.