There is a new children’s book by R.C Sproul. Looks pretty good:

http://www.christianbook.com/

In an interview he answers:

What is the message that you would like to give to parents who purchase this book to read to their children?

In this day and age, the whole need for atonement is being ridiculed widely, not just in the liberal church, but it has made its way into the evangelical community as well. People are saying that satisfaction involves God in cosmic child abuse. They ask why we can’t just rely on the love of God — that there is no need to satisfy His justice and His wrath. Through this story I want people to understand that the wrath of God is real. It was necessary to satisfy God’s righteousness in order for people to be healed. Instead of our receiving the cup of wrath, it was to be drunk by Jesus in His people’s place. That is absolutely central to the gospel.
(http://theologica.blogspot.com/2008/10/princes-poison-cup-interview-with-rc.html)