I redeemed ticket vouchers in March. When we were checking in to the resort the CM asked if I had the Canadian offer tickets and then told me that they could only be redeemed at a park. Just to test the info I stopped at the concierge the following morning and was told the exact same thing. When you arrive at the park you can go to ANY ticket booth or guest relations. You will find that guest relations has a long line but there will be several ticket booths with not a single person waiting. We exchanged ours at Epcot and did it at the ticket booth(the line at guest relations had approx. 50 people). It took about 3 minutes and passports were required.
If DS guest relations will do it for you, most likely, you will find there to be a long wait. It's always very busy there.