Actually, we first taught our Keepers’ group to do counted cross stitch on plastic canvas, but only long enough to get the hang of the stitching techniques. Most of them found the fabric in a 4- or 5-inch hoop was easier to handle. Also, we made sure the younger girls used a bigger, thicker needle. (Easier to thread, too.) Then they just used 14-count or 11-count Aida cloth.
One thing we did was to use a larger piece of cloth in a hoop, even though we were making smaller, skinny bookmarks. It was easier to handle a 4- or 5-inch hoop than a smaller one. The fabric scraps we cut off after they were finished were just a part of the price of learning a new skill.