Sorry, to clarify, are you trying to use Hopper for a WDW resort hotel stay?
I would personally save the credit for a different trip and would not book with 3rd party for WDW, ever. IMO they have one of the easiest websites to navigate for booking (when the website is working LOL), they have generous cancellation policies, and if you're staying more than one night, there is flexibility to pay over time. It is not worth saving a few dollars to get tangled up in the T&C of Hopper or another 3rd party website to potentially lose this flexibility.