I recently converted our GV room at the poly to GVC, so there are discounts. If that is what you want to do, I would call Disney and ask if there are any available. I don't know about getting upgraded at check-in. I know that it has happened, but the AKL concierge is pretty popular, I believe, so it may be full by the time you get there. If it is really what you want, I would call now and check on availability.