As you said, "and anywhere else". I say this for the lurkers who haven't really thought about it, but restrooms are another place parents need to guard their kids from homosexuals. To tweak one of your analogies a little, for obvious reasons we don't allow men in the womens restroom, so why not use the same discretion with your kids in regards to sexual harassment? No matter how inconvenient, parents must protect their kids in restrooms.
In our family, regrettably, we either accompany our children to the restroom, or send our two sons together. At the YMCA that we attend, there are obvious homosexual men in the men's locker room, and there is nothing to prevent them from walking through or hanging around the boys' locker room (as I have seen some of them do). We keep an eagle eye on our kids. Of course, it's terribly sad to have to do so. It used to be that men could just be men and women, women.