But if they don't give you the excess funds in the form of a gift card, look into upgrading your dining plan or if you think there is the slightest chance you'll return to Disney (can be sometime in your lifetime), maybe you can upgrade your park tickets w/ the no expiration option. That is a pricey option though. If you use up all your park days it is unlikely you will use all the water park options so you will each have multiple water park days to use over a lifetime. But this is only if you end up having the $700 left over and there's no other way to use it.
That is a great idea!!