GAC Passes

[SueM in MN]

Most areas are shaded in the actual line (except Nemo show at AK - that line is in the sun).
In most cases, the actual roped or divided off line itself is shaded. That is the actual line.
If you are in the area before the actual line, it may be sunny. But, in that part, the person who needs to stay out of the sun, plus one other companion could wait in the shade and then join the actual line as the rest of their party gets there.
Most attractions don't have a shaded or air conditioned area close enough to the attraction to wait that is any cooler or more shaded than the line itself.

And, the bigger sun and heat exposures to be concerned about are the places outside of lines. In many cases, you can walk inside shops to avoid some of the heat and sun getting from place to place, but can't avoid all of it.

 

[A Mickeyfan]

If they cannot be out in the sun for more than 20 minutes without getting sick, I do not suggest doing the parks in the daytime. It can take you nearly 20 minutes on a very crowded day to get from Tomorrow Land to Adventure Land.. and there are no GAC's that will help you with walking around the parks. Yes, you can wear protective clothing, and the sunscreen, but the best thing to do is do the parks when the sun goes down.