Do you have kids? I can assure you that children are quite good at automatically blocking out everything related to intercourse and other sexual acts until they reach puberty. Like an advertisement for mortgages, they will just treat it as something that is probably relevant to adults, but not at all interesting to them.
Seeing some girl getting ploughed by a slab of a guy might raise questions (which is excellent, questions are always good, because then you as a parent can guide their understanding), but it won't harm them in the slightest.
Repeated exposure to porn is a problem, but that comes from teenagers having an intrinsic interest in sex and private exploration of unsavoury websites on the internet, not accidental viewing of a naughty billboard.
Seeing some girl getting ploughed by a slab of a guy might raise questions (which is excellent, questions are always good, because then you as a parent can guide their understanding), but it won't harm them in the slightest.
Repeated exposure to porn is a problem, but that comes from teenagers having an intrinsic interest in sex and private exploration of unsavoury websites on the internet, not accidental viewing of a naughty billboard.