This is how I do them:
http://www.lazygirldesigns.com/blog/?p=2057(Not my blog, just good tutorial, LOL!)
It leaves all the raw edges from the contrast edging inside the band, and if you do a French seam, no raw edges along the long edge, either. I can whip one of these out, with piping, in less time than it takes to cut out the fabric. They are great kid birthday presents, too.
(I'm glad you're doing this charity - my son needs a service project in the Fall, and we've already bookmarked that site and will start watching fabric sales.)