J.V.
I thought this discussion would be so easy with my 7-8 year old...Man was I wrong!! She looked at me like I had sprouted a foot out of my forehead!! Very concerned I had caused trauma I found a video called "where did I come from" I haven't seen it in years...daughter is 19 now! It is a cartoon and at times awkward ( I watched it first alone) but very informative. However, when we watched it together and it was done I asked her if that was better. She shook her head enthusiastically and said "YES" with huge a relief! Hope this helps.
P.S. we always taught our kids the "proper" names for body parts. My mother-in-law (polish catholic) used to freak out! That is one of the reason's I thought the big sex talk would be no big deal...I will never forget the look on my daughter's face!