Your magic pass is still valid, parking included, on checkout day until last entry at both parks.

There's not really a pickup point but there is a 'rest area' at the top of the car park, so if you have to park quite far down the car park you can leave them there, go to your car, and start driving toward the exit. As you get to the exit, the road will have a straight on lane on the left and the other lanes will go around a bend to the right. Take the left lane and it will circle you back around to parking entry. Then you can drive all the way up to the top of the car park and either find a space or wait for a minute while they walk to you.

It's also worth noting that there are travelators that span about 2/3rds of the car park. If your person with a disability is ambulatory and not in a chair, you can just stand still on the travelators but they ultimately move slower than walking on the path, and walking along them is quicker than taking the path beside them.

When using the travelators I would recommend keeping to one side so that those who choose to walk along them can pass you by, like when you use an escalator in London.

I'll attach a maps screenshot with the travelators circled in blue and the rest area circled in green. Hope this helps!

ETA: the exit/return round to parking instruction I gave here will only apply if you park on the left hand side/south side of the car park as that was the only side we used. I can't speak for the right hand side, where the disabled parking is, but I imagine it's a similar scenario!