Your best bet might be to rent from an offsite wheel chair or
ecv rental company. They are mentioned in the stickey's at the top of the threads. We've used walker mobility multiple times and like them.
This way you can have use of the ecv at the resort, getting to and from the resorts, and at the parks, DTD, etc.
You are probably going to want to use the ecv the whole day. Start using the ecv, take it easy so you don't over do it. Take it easy and use the ecv, its better to have excess energy at the end of the day, then to be completely exhausted and tired half way thru and be completely tired and spend the rest of the day at the hotel room. You may have to spend long time at the resort, if it proves to be to tiring.
If you have never had a sergery done before, you are just exhausted as your body is healing. Of course depending on what type of sergery, and how extensive it involves, you may or may not make it the whole day in the parks.
You might want to plan to take 2-3 hour min breaks in the day, maybe longer so you can get a needed nap, or just rest for some time to recharge your batteries.
I had that sinus sergery, to open up the airways. First sergery, never expected it would take a month to get my energy levels back to normal. One experience was I went x-mas shopping, just like a couple hours. The next day I was completely exhausted, and slept the whole day. This was at least 2 weeks after the sergery. So, you might want to take it extra easy so you aren't exhausted your second day out. Or be aware you could be completely exhausted that second day.
Good luck, plan to take it super easy.
Ow yeah, the lines are pretty much mainstreamed so the ecv can fit in the lines, there are a few where you enter at MK in different, but only a handful.