Thanks everyone for your responses. Since the binding is so important for shows I think I'll go with my gut feeling here and just attach the sleeve separate from my binding. The little extra work of sewing the top edge on by hand will be worth it if my quilt hangs nicer.
As for the extra fabric samples, that's a new one to me as well. The entry form doesn't mention this at all. I'm pretty sure it isn't required but I have plenty of scraps if necessary! :)