I don't have kids too but on my part i will say when they are teenagers. This is the period of excitement when they get oa taste of adulthood and can hardly control their hormones ahahhaha..
So this will be the best time to educate them on what is happening to them and will happen in the nearest days to come. Sex education will be one of the topics at this level i guess.
RE: whats the best AGE to TEACH/DISCUSS SEX with your KIDS?