You addressed the topic well by even considering how there has been a loophole in the old ways of parenting, that though inconsequential in this times, today requires something different, with regard to sex education. If children will definitely find out this or learn it somehow somewhere, why not teach them yourself as a parent and in the best, healthy way possible? It will do you both good. They will love able to open up to you on matters that pertain to it and they'll do that comfortably without feeling somehow about it. It's a knowledge children of reasonable and understanding age need.