My son, who is autistic, gets a GAC. I can honestly say, for some attractions (where we can enter through the exit), it really helps him. However, using a GAC at attractions that have a fastpass line isn't as helpful for him because there are still so many people around him in an enclosed space and/or in switchbacks. Sometimes he's fine in the fastpass line. Other times he'll hyper focus on something or someone while in line (people breaking the rules, kids swinging the chains back and fourth, etc) and he can get stuck on that one thing for hours. That's when we have to take a break and get outta Dodge for a while - lol.
That being said, I hate him having or needing a GAC. Why? Because I know there will be people thinking he doesn't need it....that he's just faking to take advantage of the system. It makes us feel kind of...guilty, even though he's using the GAC legitimately. I know I shouldn't care what other people think, but I can't help it. I do care.
That's why I would LOVE it if Disney did require proof. I would be more than happy show Ryan's letter of diagnosis, IEPs, or whatever else is necessary. That way people can't take advantage as easily, and those who actually need a GAC won't be glared at with suspicion.
On the bright side, because Ryan hates having to use a GAC (he feels it makes him "different" than everyone else) he has worked hard and made great progress in not becoming hyper focused as often.
Kind of ironic that someone who needs a GAC hates having to use one.