Big Thunder - Get a Return Time. When you come back, you will be boarding at the exit
Jungle Cruise - Get a Return Time. See a CM near the regular entrance/Lightning Lane entrance. When you return to ride, go to the same place and let a CM know you have a Return Time. You have the choice there to ride the accessible boat or to transfer.
Mickey Runaway Railroad - both the Standby and Lightning Lane are wheelchair accessible. When you get close to the boarding area, your group will be directed to a dedicated accessible load area. You can bring the wheelchair as close as you need to the ride vehicle, then transfer and the CM will move the wheelchair away for you.
We found it challenging to transfer our daughter due to the narrow door opening and needing to get over a lip to get into the ride vehicle