Their daughter can be a serious Christian who gently promotes concepts like tolerance, charity, love, forgiveness, and morality.
The whole "kids can be the opposite of their parents" concept could be a real hoot.
Actually I have known some people like that too. Parents were unreformed hippie slime from the 1960’s, kids were decent, honorable, straight-arrow Christian types.
Watched "The Good Wife" lately? (actually the Christian daughter was a very small part of a few shows last season)