I'm going to go out on a limb here and recommend your mother
get an ECV. She will be totally independent that way, no one
will tire from pushing the chair. I use an ECV due to bad knees
and sciatica. I usually park it outside the rides and walk in as
I can do that much standing and walking. Park maps have symbols telling which allow ECV, which just wheelchair and which
you have to move to a seat on the ride without either.
Few attractions have a chair or ECV being an advantage anymore,
so few, I can't remember any specifics but there are a couple
of them. ECV rental at the parks is about $30 per day but well
worth it at the end. You always have a seat, Grandma can carry
lots of bags under her legs, there is a basket on the front too.
Grandma can also head off for FP to attractions while some of
you enjoy a thrill ride she's not interested in. I rent mine from
Walkers outside the parks so I'm assured of getting one and
can ride it from the parking lot. This year, DS was just getting
over the flu so he rode on my seat in and out of the parks-not
recommended but ok in a health pinch(At EPCOT, we got him
a double stroller as he was tired). I got ECVs for DMIL and
DFIL when they went with us a few years ago. They were hesitant at first but by the end of the first day, they realize what
a bonus the ECVs were and that they could never have kept up
without them- also that they were totally free to go off and do what they wanted while we did something they were just not interested in. IE, they shopped, we don't usually.