1. The Word of God
2. Our souls.
I strongly believe that we should train up a child in the way he should go, so that when he is old he will not turn from it.
Joseph can already pray on his own, lead us in worship and tell us most of the Bible stories. I thought it would be good to start him on a more systematic and consistent daily quiet time.
Not too deep, nor too simple - it has very practical topics, starting with "Who created God?" and other topics like "What is a conscience?" , "When we're bad, can we still pray?" , "Will God give children toys if they ask him for them?", and plenty more.
The topics look interesting to me as well. I hope this starts Joseph on a life-long love journey with the Word of God.