You could always plan to do indoor activities during the day and then at night enjoy the rides that may not have adequate coverage in their lines.
This is a great suggestion!! I have a friend who has had lupus for 20 yrs. Her family typically goes during Spring Break, and this is exactly what they do. Relax at the resort during the day, then head to the parks around 5, and stay til 12 or 1. She said the parks really empty out after 10, and they can walk on pretty much everything late at night.