you have to park at the TTC and take either the ferry or monorail, but the bus goes directly to the park entrance.
it is a bit of a walk from the HC parking to the TTC - if your wife can step up into a tram, it may actually be faster than the HC parking area.
your wife may want to speak to her dr about other options for in the park. you will be away from restrooms at least as long when waiting for a ride (even if there is no one in line). there are no front of the line passes anymore for people using wheelchairs or with similar needs (that changed a few years ago), so you and your wife will have to wait, even if you use a GAC. she may need to look at options, just in case!
also, most attractions are longer than 10 minutes (philharmagic is 15 including preshow, GMR is 20ish, etc) and there is no options of bathrooms on those rides. unless your wife can go 5-10 minutes without a bathroom, she will be unable to enjoy a lot of the attractions without exploring other options.
i dont know how your wifes condition presents itself, so i am just trying to cover all the options
(i say this as someone who, while not having MS, i have a condition that mimics it, so i understand about sudden bathroom needs!!! my best advice is PLAN AHEAD!)