I have MS. I will admit that I'm somewhat lucky, as it hasn't affected me too much, apart from my initial issues when I was first going through the diagnostic process. I definitely have some endurance issues, and am not as active when the sun is out, and I tend to tire easier.
We flew into SNA, and took the
Disneyland Express, which dropped us off right at our hotel. (They will drop off maybe 100 ft from GCH.) We didn't rent a car, because there wasn't really any reason for us to rent a car, IMO. There were shuttles if I was really having a bad time, and of course, renting a ECV was also always available if I needed it.
Biggest things:
(1) Be willing to use an ECV if you need it. There's no points for toughing things out! And you will enjoy it so much more if you aren't pushing yourself!
(2) Water water water water water. Did I mention water?? I didn't drink enough, which I think is part of the reason I had a hard time at some points.
(3) Sunscreen, light pants and light shirt, sun hat! Not the most fashionable, of course, but that sun can be something else, and it seemed to me that the sooner I shielded myself from it, the better.
(4) Afternoon rest areas: Aladdin, Turtle Talk with Crush, It's Tough to Be a Bug, Captain EO. These areas were my energy rechargers when I started feeling fatigued.