he can stay in his chair, if you go to Monsters, Inc. and Toy Story Midway Mania. You have to go thru the regular lines for both (which is a real pain, all the back & forth thru the lines, but when you get to the end, just tell the CM he needs to stay in the chair and they'll get the vehicle for you.
It can sometimes take quite a while to get the wheelchair vehicle to come back around, but it will get there eventually. For TSMM, you have to go further down the queue area, past the stairs, to get to the wheelchair end of things, and for MI, you just go a little further over from where they doing the regular loading.
It would be a lot easier for us, if they'd allow us to go thru the exit for MI and go in where there is a gate near the entrance to the TSMM queue, since it puts you in the area for going down to the wheelchair loading area, but they don't.
Also, he can stay in his chair to see the Aladdin show, but the area where they have the wheelchairs sit is VERY slanted! I couldn't stay in my chair, because the pitch puts you way forward and my brakes wouldn't keep me from moving, straight down into the backs of the seats in front of you, because of how it slants down! So I had to get out of my chair, sit in a seat and then the CM took my wheelchair away. They won't bring the chair back in for you at the end, you have to have someone in your party fight the crowds getting out, to get out to where they put the chairs, then have to fight the crowds again, going against traffic, to get back in, to get it to you, so you can exit, after all the others!
It's a real drag, as it would be so much easier and make much more sense, since the CMs know when the show is ending, if they could bring your chair back in to where you're seated, but they won't do that!
Something else for DL, it's not a RIDE, but the castle walk-thru has an alternate viewing room, as you're going into the castle area, on the right side. It's certainly not the same as the walk-thru, it's a video, but it's something else you can do without having to get out of your chair for.
There is a special wheelchair vehicle for the Pooh attraction, so he can stay in his chair for that and you can sit behind him in the same vehicle.
I haven't done Pirates in a long time, and seldom do it in general, since you have to climb down into (as well as back out of) the boat to ride it and it's really hard on my knees and back to do that. It might be really difficult to lower him down into and back up out of the boat, unless you have super strength. The CMs will NOT help you do this, so you might want to rethink doing it.
Also, for Mansion, you'll get to go down the side of the hallway, next to the windows, to get to the Doom buggies, but you'll have to ask them to stop the belt, so he can transfer from his chair to get into the buggy. You'll stay in the vehicle past the regular exit, come back around to where you were loaded in, then go back down the side of the hallway and wait for the elevator ("stretching room") to unload, before going in and riding the room back up to the top to exit. It's interesting to watch the paintings go back to their original positions.
Getting around the parks in general can be hard to do, especially if it's at all crowded, since so many people there will run into the chair without looking, run right in front of you to get past you, etc. There have even been parents who will look, see us coming, and then push their kids out in front of the chair, to get past us! It's not a very fun thing, for the rider or the driver.
Going in June will be crowded, as well as very sunny, so you'll want to consider having him wear a hat, sun screen or have some other form of sun protection. I'm very sun sensitive, always have to wear a hat and sunglasses, so I'm always looking for shade to wait in, instead of just sitting in my chair in the sun, while we discuss the next thing to do or whatever.
If you have any other questions, please feel free to ask!
I hope this info is helpful and that you have a good time.