I often get questions regarding book recommendations for teaching children about sex. Here are a few I have found to be helpful:
What’s Going on Down There? Answers to Questions Boys Find Hard to Ask by Karen Gravelle (geared towards boys 10 and up)
It’s Perfectly Normal: Changing Bodies, Growing Up, Sex & Sexual Health by Robie Harris
It’s So Amazing! A Book about Eggs, Sperm, Birth, Babies and Families by Robie Harris
These are not books put out by the church or LDS authors. Therefore, the messages surrounding masturbation and homosexuality are normalizing and not presented as “sins.” My recommendation is to read through any sexual education book first yourself. Then, as you present it to your child, you can explain things from the parenting perspective you feel comfortable sharing. These more “worldly” views are going to be around your children anyway. It is a powerful parenting opportunity to be able to say, “Here is what this book says about this matter. I agree with this but not with that. What do you think?”.