We used three days of unused WDW hoppers last year in May and had no problems at all. If you do, I recommend going early because you will have to bring them to the gate and let the CM know that they are WDW tickets. You will be asked to step to the side and another CM will take the tickets and call to verify what is still good on them and let you know what you have left to use. You will be given back your WDW tickets (if there is anything left, we had some water parks) and a DLR hopper replacement.
It's easy and it actually didn't take too long. I thought we'd be there forever but he came back pretty quickly every time.
We love DLR but WDW is so different and awesome too, you'll love it!
Have fun no matter what you do!