My general preference for children is to give them physical books because of the developmental advantages of tactile interaction, there are families who also want their children to grow up with a familiarity with computers well ahead of the curve. As I've discussed in the past, we need to have a balance to ensure that our children don't become third-class or fourth-class citizens just because they weren't allowed to interact with technology.
That being said, Nor Sanavongsay's children's book "A Sticky Mess" is now available for Kindle. iBooks and iPad versions are coming soon! It's been reformatted to take advantage of the Kindle features and it's available for $2.99. You can't really get it autographed, but at the same time, it's harder for your kids to tear the pages, so that's one advantage.
Hopefully it won't be too long before we see the follow-up childrens books from Sahtu Press. They're trying to develop a great catalog but they're also still a small press, so any help now really makes a difference. Get a copy now for the holidays!