We used our GAD vouchers in January. The options were a one day one park ticket, a fastpass, or a souvenir mickey head. If you have APs, then I would recommend either trading in one voucher per day for FP or get one fast pass and one souvenir mickey head. The way the fast pass works is that they give you enough FPs for your entire party (with just one GAD voucher traded in). Along with that they have a list of rides divided into two groups. You can use your FPs at any three rides from each group. When you insert your FP at the ride, you are able to go on immediately and do not have to wait for a later time. The souvenir mickey head is great too. It comes with removable pins. My son loves his and feels proud about volunteering every time he looks at it.
Have fun on your trip.