The Kindle Colorsoft is a small, but sufficient ebook tablet. The ereader will support kindle books, and will be able to email other ebooks to the reader. There is an email address attached to the Kindle, but it is usually a very complex address that will be nearly impossible to remember. With that said, I would recommend to the child to use an email address that would be easy for them to remember to forward to their Kindle. An example might be to setup kc@site.tld to go to their complex kindle address.
I will encourage any foster child to invest in the time of finding good books to read. Reading increases literacy, and improves the imagination, and who can argue with that? The Kindle Colorsoft is small enough to hold in one hand, and make it comfortable to read. Who knows, it might even be more comfortable than holding a regular book. The Kindle will also be theirs if they should leave my custody.