I have the Queen Homeschool materials-G-d's Plan for Growing Up Series. My dd hasn't asked many questions yet, but my son, the ever inquisitive one, is the reason I got them. I didn't like the more mainstream popular Christian sex ed. materials out there as I thought they gave too much too soon and had imagination enhancing drawings, if that makes any sense; my son didn't need to see a baby being born at age eight, IMO. He has read throught he boy to man book and the Baby book from them.
I like them alot, they are very clear, in Black and White, simple drawings; very basic, G-d Honoring, Marriage honoring; A starter book I say, then move forward from there. I also don't plan on a "curriculum" per say, but use whole books written to encourage purity and modesty (there are several on the Queen site). I also just talk about things as they come up.
Two other books I came across are "The Miracle of Change" and "The Miracle of LIfe" by AMi Loper. I haven't read them yet, but they are next on my list and are directed towards pre-adolescent age. There's one other recommendation I came across a couple of weeks ago that I will look for as it looked real good.
HTH,
Rachel