I might also look into Lulu and such. I'd have to look again to remember the names, but there are a couple of on-demand printers that can bind your writing into a book, plus the photo companies that offer photobooks...if you take a few photos for illustrations, you can enter the writing as captions basically, as a text box on a scrapbooking page.
I would show him how he could make a whole anthology to share with grandparents if he wants, for much, much cheaper. If he never gets around to it, that's okay, too.