So I (actually my wife) ended up getting the set on the left in the picture - http://www.potterybarnkids.com/products/headphones-w11/
They seem to work just fine. I'm sure we over paid, but it was convenient.

I agree that overear is the only way to go. Otherwise the slip off or out to easily. He did very well on the flight and wore the headphones for a couple of hours each way. I even got to have a glass of wine on the flight. Thanks iPad and headphones!