No, you can't link the kindle books to the Kobo - Amazon make their ebooks in a format that can only be read by the Kindle ereader. The Kobo reads the Epub format, which is a generic format across the ebook industry.
If you decide to keep the Kobo, he can get books from the following:Kobo booksGoogle Play BooksBooks on BoardFishpondBookworld
Some of these stores such as Kobo Books and Books on Board offer specials periodically such as 30 - 40% off. Google for coupon codes before purchasing to see if there are any offers open.
Also have him check out his local library - many libraries now lend out ebooks in Epub formats for free via their websites. Our local library happens to have an excellent collection but not all public libraries may be of the same quality.
He would either download these books via the wifi or via his PC using Adobe Editions
which can be downloaded for free.
This post has been edited by Henndigo: 31/01/2013, 02:21 PM