Definitely get a GAC because it will help. If you have a problem with a particular queue like the one visiting Mickey, talk to the CM at the attraction. There were a few queues my son doesn't like (dark and noisy) and he does not like to wait in super crowded lines because it makes him panicky. So, when we visited characters that I knew he couldn't handle the line, we talked to the CM and the rest of the kids got in the regular line. When they got to the character (usually with Dad), he (and I) went in the exit. Even if you don't have other kids getting into line, one parent could do it. It is definitely worth talking to the CMs at the attractions and having the GAC. Of course there is no guarantee that they will let you do it, and it could depend on the crowds, particular CM etc, but we had no problems finding a way to accommodate his needs. (It didn't cut out the waiting, but it made it possible for him to do it!)