Sorry, OP, but I agree with the others. Rent an ECV (or, if she's a bad driver or intimidated by the crowds, a wheelchair that you will have to push). Better to swallow ones pride and be able to enjoy a longer pain free day in the parks, than to struggle along on one's own. Look on the scooter as a necessary aid, much like a pair of reading glasses.
As for making your trip a special one (congrats by the way), be sure to get an anniversary or celebrating button at your resort or a guest relations desk. You'll get a lot of Congratulations and Happy Anniversarys from the CMs. Book a nice dinner at one of your favorite signature restaurants, maybe with a bottle of bubbly. Or go whole hog and book V&As for a truly memorable evening. If you're staying at a Port Orleans resort, you could book a ride on one of their horse drawn carriages. The ride along the river can be very romantic.