Allow parents to see a movie solo to see if it is appropriate for their kid. Then give only charge them for the kid’s ticket if they do decide to bring the kid on another day.
This would have earned movie theaters a fair amount of money from me if it was an option. If I watch the film, and decide it’s not for my kid, they still got a ticket sale they wouldn’t have otherwise. If I decide it’s okay for my kid, and I come back with them to watch, they get an extra kid ticket sale (not to mention inevitable concessions) by comping me for re-watching a movie I just saw.