Ask HN: iOS app instructions for children

My 6 year old nephew is interested in making an iOS app. He has no knowledge of programing languages or what it involves. He is very fluent in using computers and a quick learner.

Most books I know for Objective-C and app development are targeted at adults. Does anyone know of any good books or video tutorials for children of the age of 6? If there is none, I plan to create some instructions for him myself, but having some guidelines on how to instruct children would be amazing. I've never taught to children, only coached and mentored members of my engineering team.

Thanks in advance.