Let's start with
Disneyland. While the GAC is not necessary in your case it is easier to get one at the beginning of the day and get the disabled guest booklet. As for lines it depends on the time of the year. As with WDW you may have to wait for the ride to cycle or for other disabled guests to be loaded.
Fantasyland, Toontown and Tomorrowland areas
All disable entrance are outdoors and not covered. Alice in Wonderland, Tea Cups, Pinocchio, Snow White, Dumbo, Casey Jr., Bobsleds and Canal Boats have the disabled entance is at the exit where you wait in the sun. Small World enters at the main entrance and was not covered the last time I was there. The monorail uses and elevator and there is a spot you can get out of the sun. Star Tours uses a side entrance and is indoors once you are let in. Space Mountain requires going toward the exit then through corridors so it is shaded then indoors. Innoventions requires sitting in line which is shaded part of the day by the build but is outdoors and usually in the sun. Honey I Shrunk the Audience usually is shaded and loads large groups so not much of a problem. Train stations have a covering but sometimes you still get sun and the Main Street Station is not disabled friendly and not stroller friendly.
Adventureland, Critter Country, New Orleans Square, Frontierland
Pirates is indoors through the exit. Jungle Cruise is outdoors, shading depends on time of day but generally the wait is not too long. Big Thunder is outdoors and through the exit. Splash Mountain is out doors in a few places and through the exit but there is an indoor area where photos are shown that you can wait probably or rest. Haunted Mansion is outdoor line with not much shade usually. Rafts and canoes were outdoors. The Mark Twain takes lots of people, has some shading and has short lines usually. The Golden Horseshoe has some shade nearby and the family can hold a spot.
DCA
DCA will be undergoing 5 years of renovation and construction. It is very disabled friendly and they try to make everything so that all guests have to stand in line. California Screamin' used to have wheelchairs enter through the exit because the loading is from one side then the guests exits from the opposite side. All rides have lines outdoors and uncovered. Grizzly Rapids there is a gate inside to your right and it is that area that is sometimes shaded. A big loading bay where the boat parks and waits for the disabled guests. Unlike Disneyland that park can get HOT. Disneyland has trees and shade spots but not so much DCA. Check with
youtube. The shadier way to the back of the park for me was up past Soarin and around to Grizzly Rapids.
