Most Recommended: 

Before They Ask: Talking with your child about sex from a Christian perspective (Abingdon Press, 2005) 
A guide for talking with preteen children about sexuality with honest and factual information.

Parents and Grandparents as Spiritual Guides: Nurturing Children of the Promise, by Betty Shannon Cloyd (Nashville: Upper Room Books, 2000. ISBN 978-0-8358-0923-2). Explores the ways parents and grandparents can introduce children to God.

Read the full list on page 2.