Just adding to what the others have said.
Parking will not be an issue.
If you haven't yet looked, my best suggestion would be to check out the disABILITIES FAQs thread. In post #2, you will find rental information for
ECVs and wheelchairs in case you have not rented one yet.
Post #3 has links to helpful information, including links to the online version of the WDW Guidebook for Guests with Disabilities - although I have to warn that they reformatted them to make them look nicer, but in the course of doing that, they removed some information, repeated some and have copies of some parts where they don't belong. Once you get to the parks, you can get a Guidemap for Guests with Disabilities at Guest Services. It looks the the usual map, but includes information about what to do for handicapped access at each attraction. If you look at the partially completed Epcot FACs thread, you will find information and some pictures about Epcot.
Keep in mind that both of you will be more tired just from pushing a wheelchair around, transferring and all that. If she has a wheelchair with an elevating footrest (which I agree with a previous poster will help keep her leg from swelling) you will need the footrest down in order for the wheelchair to fit inside some if the rides cars where the wheelchair can be loaded directly into the ride car. If she gets tired and needs to rest lying down in the cool for a while, there is a First Aid station in each park where she could do that. If she needs your help in the bathroom, there is a Companion Restroom in First Aid and also at locations outside First Aid in each park you can use. The locations are marked on the Special Needs map. They are single toilet, unisex bathrooms with a door so someone who needs assistance can be in with the person to help them.
So take it easy, take your time and go out and have a great trip.