Depending on where in the handicap parking area you end up, the wake may be quite far and there is no tram service. We also found most if the courtesy whewlchair parking corrals were empty when we were at WDW the last 2 weeks of October. If you don't have a wheelchair or
ECV with you and she is able to step up into the parking lot trams, you may actually be better off parking in the regular lot and using the tram.
If you have an ECV, you will need to park in the special lot ( more info about that in the FAQs)
You will also want to check with her to see if she is comfortable with the idea of using an ECV. they are pretty easy to learn to use - she could practice ahead of time at a store like a grocery store,
Walmart or Target. The ones in the stores are very large and have a shopping basket on the front. If she is comfortable driving one of those, the park or off site rental ones will seem very small and much easier to drive.
Some people do not feel comfortable driving an ECV, especially if they don't drive a car or have any vision or hearing problems. Drivers of
ECVs need to be alert and ready to stop at any point because people can and do step out in front of you with little warning. My FIL was experienced, but would not drive an ECV at MK because he felt it was to congested for his comfort. Even though it is physically less tiring to use an ECV than to walk, many people do tire from the need to be alert all the time, so you may still need to rest frequently.
Also, some older people have difficulty with their eyes adjusting to the darker inside conditions when coming into buildings.
Also keep in mind that many older people choose not to drive their cars at nigh because of night vision changes, so she may have some feelings about driving one at night.
Given all that, some people decide they would be more comfortable being pushed in a wheelchair. It is a very personal decision. Some like independence and would not want to be pushed by someone else. Some like the idea of the ECV.
Another thing to keep in mind is that not every elderly person needs an ECV or wheelchair every day if they are normally very active and have no health issues. We have taken my mom and MIL with us on many WDW trips. The last was Spring 2011 when both were 82, but both are very active, walk every day and were health.
We do not tour from opening to closing and we do use a pretty leisurely touring style. We also alternated park and slower days, which helped.
This only works for a few people, but did want to throw it out there as a possibility that she may be able to do something like park an ECV and walk or even walk a specific park like MK for a short day if she's healthy and in good shape, you don't push it, she will speak up before she's too tired and everyone is willing to stop and rest. if any of those are not met, I would just count on using the wheelchair or ECV.