Another option is to get your package with just a one day base ticket for each person. When you get there, have your package ticket removed from your room key and issued as a paper ticket. Put that ticket away and save it. It will never expire and can be used (and upgraded to a longer ticket if you want to) another time. Then, use your GAD voucher for admission the first day you go to the park. Upgrade the GAD ticket that day to whatever kind of ticket you really want for your trip.
It doesn't save any money this trip, but next time you go, you will already have a one day ticket that can be upraded to a longer ticket for that trip. Since Day 1 is the most expensive day, it will help cut your next trip price.
We are doing this in September. Basically, it is a round-about way turn your GAD ticket (that expires Dec. 15) into a ticket you can keep as long as you want and use whenever you'd like.