I'm dealing with a "situation" where I can't really ask his Mom and step-Dad to let him use their credit card (my son's divorced wife and her new husband), so that won't work. He is too far away for me to feel comfortable turning him loose with mine and I won't be there to enter a password.
I have a gut reaction against calling anybody's tech support, but maybe that's the best bet. It looks like kids can buy stuff using gift cards. Amazon limits app purchases to kids older than 13, but I don't find anything like that on Barnes and Noble's site.
Thanks for the replies.