Do you really need the delux plan? Thats alot of food. I have found the regualr plan works just fine. I don't know if thats a good deal as I don't know how much the deluxe plan is, nor do I know how much it is to stay at the Poly. But I would say it sounds like it might be. It would cost My family, of 2 adults, one child on the regular dining plan, at a value resort, with parkhopping tickets, a little under 1300.00 for 5 nights.(If I remember right)
You can go to the Disney site and play around with the prices and see if it is a deal or not.