I had to laugh at "non-willies"! I know what you mean, I only have sons and my youngest was very troubled when I explained one day that I haven't got a willy! He wanted to have a look! Ok, we're an open family, but there I draw the line!!!
I can relate where your own mum is concerned. My mum was mortified when she had to discuss anything about the body, sex, periods, and so on. You're lucky you at least got a book I was lucky, I had older sisters who helped me out. So, I felt the same way as you when I had kids, I was determined not to make anything taboo with them, and trust me, it has gotten easier as time has gone by. I felt awkward at first, but I did make every effort to hide my embarrassment, and it obviously hasn't shown, because my 10 yo comes and asks me and his dad about everything, sometimes things that could make your eyebrows hit the roof!
So, keep doing what you're doing, because it will have great results. Its really nice when you know your kids can come to you without feeling embarrassed.