Ok, that was absolutely awesome. I can't stop crying. Not just because of your son's reactions, but yours as well. You see, I know exactly how you feel. I too have a son on the spectrum, he is 10 and has Asperger's Syndrome. I was able to keep it togther until I saw your picture with Goofy - then it was game over and I have been boohooing on the couch ever since.
I don't think people realize that the things that they take for granted everyday become so magical for us. When your son was interacting with the different characters you suddenly get to see your child come out of himself. I don't think even the CM's even know the depth to which we (as parents) are touched when such wonderful things happen to our children.
Your DS is adorable, enjoy him, remember to keep your sense of humour and treasure those very wonderful memories...
See you on freap chat - and thanks again for sharing, it really made my day.