DVC members can still pay for the plan at check-in. I believe the new system allows prepayment, but doesn't mandate it. Yet.
As far as I know, a Disney gift card is an acceptable payment at any Disney-operated location. I know they can be used to pay off charges made to a resort room, so resorts are capable of accepting them.
I'm curious, though. Why gift cards? If you don't have or want to use a credit or debit card, why not just cash?