8y is to old to start talking about sex,.by that time the are already abused because the didnt know(as in op) .

with my son we started talking about when he started asking arround 5 y old(wich means he is interested and willing to listen) because he hears the news as well on TV and radio.

now almost 7 he knows what he needs to know and how to react if somebody tries

when my 3 old girl starts asking about we will tell here as well,.and she goed then to self defence class as well,.(to learn how to kick and scratch to leave marks)