Now that I think about it, the issue of a sufficiently robust ebook for children has already been solved. The One Laptop Per Child program (
http://www.laptop.org/) distributes extremely robust and very simple laptops to children in third world countries. They could, of course, be used for reading books -- I think there's even a specific mode for doing that. It's a bit pricey to buy one in the US though, I think about the price of an ebook ($400?)
On a slightly different note, does anyone think that schools could save money long term by switching over to ebooks rather than pbooks? Or would it just be more expensive overall?