Where do Babies Come From? Both the boys' and girls' version of this book for 7-9 year olds (available from Concordia Publishing House) are awesome. Both gender based books revolve around a birthday, a trip to a museum and the pregnancy of a Mom in the story. The vocabulary covered includes uterus, navel, umbilical cord, pregnant, nursing, ovum, and sperm. I am including 2 quotes below to show you how tactfully this book covers the answer to the question, "Where do babies come form?"
"God planned it so that it takes both a mother and a father. You see every baby begins when two tiny parts join together and start to grow. One of these parts comes from the mother's body. It is called an ovum. The part that comes from the father's body is called a sperm."
"At special times, they (Mothers and Fathers) like to hold each other very close. God made their bodies to fit together in a wonderful way. "
You'll find really positive references to the opposite gender in each book. The Dads and Moms on the Parent Ministry Team I work with who read this with their own sons and daughters in their homes felt like it was a positive and empowering experience.
That's the plan... to encourage parents to consistently and thoughtfully shape their children's moral, spiritual, and ethical thinking so that they can be responsible and well educated decision makers in every area of life as they grow older.
All of life fits together. Love and Logic classes teach that it is good for children to make mistakes and experience the consequences of their actions while those consequences are still quite small so that when they are older (and the consequences are much bigger) they have and understanding of personal responsibility.