wanted to report back with my experience at the POP on Oct 2:
when I checked in I asked if we could apply all our GC's and Rewards cards to the room account and the CM said no problem. they have a piece of paper that they track the each payment as she applied it to the account on the computer and then handed us all the cards back. If for some reason we had balance left over (ha!) if would be refunded back on one of the GC's. We did leave a CC on file so we could do the express checkout as I figured there'd be something we forgot about (and there was but it was nice leaving Disney with just a $60 charge for pictures

) but the CM had said no problem to the GC's before we put the CC on file.
however, i found out that this year you can no longer charge the Food and Wine GC to your room account - it has to be cash or charge. So that killed our plan for convenience. that was part of the reason why we wanted to put all the little cards on the room account so we didn't have to keep pulling something out of our pockets to pay and risk dropping stuff. we planned to just charge the little wrist GC to the room but the CM's at the Festival Welcome center made it seem like it was a change for this year. hope they don't keep it.