Hahahahaha! Actually, perhaps this is terrible, but my wife and I used to get a sadistic kick out of seeing our children hide their eyes if a sex scene appeared in a film. Not that we ever showed them top-flight smut fests like In the Realm of the Senses, to be clear. Just comparatively mild interactions in the likes of Top Gun, Titanic, Dances with Wolves, The Terminator etc. These days, they're getting more relaxed about it (they're now 18 and 14).