All of the buses can handle at leat two wheelchairs or
ECVs. Some of the newest ones handle three. Possibly if a bus already has one person in a chair ahead of you the group will have to break up.
You cannot park the ECVs outside overnight for several reasons. One is that you need to be able to plug in the
ECV to recharge the batteries; for most rentals you have to connect the charger to the ECV and not directly to the batteries. The other is these are corridors which should not be blocked. And third is that you are leaving a piece of equipment worth a couple of thousand dollars outside where anyone can fool with it (and at Coronado you tend to get convention groups where the members are "well lubricated" late in the evening.
Normally there is no problem fitting one ECV in any size room, even the value resorts. At a moderate it can also be doen, but some furniture, such as a table, may have to be moved. Note if you will be putting both on one room, I would suggest bringing a power strip with about a six foot cord so both can be plugged in.
You cannot get two standard size ECVs in one car. We tried this about ten years ago, and it would not work in any rental car, even a Cadillac. We ended up with one family taking a bus and the other using the car, and we would meet up. Unless we were going to another Resort for dinner and only needed the ECV for one person and then all six of us would fit in the car.
I was able to get two ECVs in a Ford Taurus, but mine was a standard size and Judy's was a transportable Pride Go-Go. However, not only was the trunk full, but both seats were in the car's back seat and the batteries for mine were on the floorboards in the back.
You might have them go to a
WalMart (or similar) or large grocery store and practice using their ECVs. Just be aware that the rentals, especially from off-site, are much easier to use than store ones.
And if your mother feels she cannot maneuver the ECV onto the bus there is no problem in having someone else do the driving. Note that because of center of gravity locations it is
unsafe to sit on the ECV when it is parked in a bus. Always move to a regular seat after it is parked.