The web certificate can be used for ANYTHING, it is a mastercard account. Once you redeem they send you an email with a link to webcerts, DONT delete it!!!! YOu have to set up an account there and then they will put in your mastercard number. Be aware that they will charge you for NO ACTIVITY, so use it or loose it. Then you can call WDW and use that CC number and balance to pay part of your room.
BTW, most TDS' are out od Disney Dollars, and they have no idea if they will even get them again, according to a cast member I know.