Thanks again for the advice. My DH downloaded tChess Pro (thanks mithawk), and DS and DH both seem to like it. (I suspect DH got the idea from this site, but I forgot to ask him...)

S-T, the chess.com sounds fun too. FYI - have your DS read all the review on the Fritz and Chesster app for iPad before you commit. And if he gets it anyway, I'd love to hear your/his review here.