I travel all the time, sometimes I have really bad days during the trip, and sometimes it goes without one problem. Some things that I try to do is make sure I have enough meds for emergencies, because once the pain gets out of hand it is hard to enjoy anything.
One thing you might check on is a power chair for both of you. This will take a lot of the stress level down just knowing you dont have to walk everywhere, and Disney will accommodate you on the rides you might want to go on.
Above all try to have as much fun as you can because those memories really help out after your back home. Glad your your going to get out and see some sights!