This for sure. I’m sure she’ll suck it up as long as she can to see her kids happy, but that’s not necessarily a good thing.
If you’ve heard of the “spoon theory” of disability, consider she only has a max of 5 spoons a day. She can save up spoons (to a degree) and borrow on tomorrow’s spoons, but eventually she’ll run out of spoons. When she runs out of spoons the trip is essentially done for her. The goal is to make sure she still has enough spoons to enjoy this trip.
We are *very* well acquainted with Spoon Theory at my house.
That's why I'm going to encourage you to get a wheelchair for her. An
ECV will "cost" her energy because not only will she have the physical act of driving it, but she will have to be hyper-aware; sadly, so many people are on their phones, or taking selfies, or posting to Instagram these days that they often (seriously) walk right into the path of scooters, wheelchair, strollers - basically any mobility device that is below eye level. There are long time members here (myself included) who have experienced people walking *into* our scooters (and then blaming us because they weren't paying attention) I feel like she would be able to conserve her energy far better by being a passenger and not a pilot; there is an actual physical and emotional toll from piloting a personal mobility device at WDW, and that's a spoon (or three) she doesn't need to spend.
Since it sounds like you will be staying offsite, First Aid in each Park will become your friend. Download the My Disney Experience App for your phone, and find the location in each Park *before* you need it. You will be able to get paper maps at the entrance to each Park. I have found when planning a trip, just going over the map and finding where things are can be helpful; it can help prevent needless criss-crossing of the Park. And with kids, knowing where the closest bathroom is, and where the nearest quick service (counter service/walk up/fast food style) is will be important. (Also, every QS at WDW gives out free ice water - you just have to wait in line)
Additionally, ask for Park Hoppers if they aren't automatically provided by the Dream people - that way you could go to one Park in the morning and return to a different Park later in the day.
I know this sounds corny, but my first trip to WDW was in July of 1972. It was my 12th birthday, and the Magic Kingdom had only been open for a few months! It was *quite* a different place then - EPCOT was still on the drawing board, and Hollywood Studios and Animal Kingdom hadn't even been dreamed up yet! Even though we had only a day and half at the Magic Kingdom (this is back when if you bought your tickets after 3pm, you got the next day "free" LOL) we still didn't get to do every single thing. But it didn't matter, because there was a parade to watch, and hot dogs to eat, and an amazing candy store on Main Street where you could stand on the sidewalk and watch them make the candy inside, and it smelled like heaven! What I really remember from that first trip is how beautiful and magical and amazing everything was. And how even the most mundane things - like eating lunch - were somehow wonderful because we sat at Casey's Corner and looked at Cinderella Castle!
We were at Disney World! Kids often don't remember a lot of the details about their first trip to WDW because it's just so overwhelming! (some adults feel the same way LOL)
My point is this (and yes, I do have one) - There is *so* much to see and do at each Park, so worry less about a hard and fast "to do" list, and focus on keeping your sister as comfortable as possible. If she is OK with one of you taking the kids to go do things while she rests, that allows the children to take fuller advantage of their time, and ride some rides, and maybe see a few shows. But there are so many quintessentially "Disney" things to do that don't involve lines, Fastpasses and queues - like having a Dole Whip in Adventureland, and riding the Monorail, and walking through Cinderella Castle. She may only feel like going around and seeing everything - and that's OK, because we know that just being there has a cost for her that none of us can really comprehend.
And as a previous poster in this thread mentioned - I know it's hard to believe, but there is a very real phenomenon that many of us have seen first hand with terminal patients at WDW: They get a "boost" or an "energy burst" that is unexplainable by any logic, and they somehow have a trip that exceeds everyone's expectation. It's been seen in both children and adults, and there's no real explanation for it. It's just... magic. I'm not guaranteeing you that it will happen, just making you aware that it is a known "side-effect" for some terminal patients.
My heart and prayers will be with you and your family.