My guess is that the OP's family has "regular" APs and would like to upgrade to the
DVC-discounted PAPs. They should be able to basically trade their regularly priced APs for DVC-discounted PAPs. Then they will be able to visit DQ, the waterparks and PI for no additonal cost during their upcoming trip.
AFAIK, you can still do this. However, do not expect any refund from the transaction even though the price of the DVC PAP is less than the price of the regular AP.
Best wishes -