The bottom line is that if it makes the trip more comfortable for your wife, the wheelchair will make the trip MORE magical, not less. If she is exhausted, hurting, or simply can't move fast she won't be able to enjoy the trip. Don't worry about what others may think. To look at my 87 year old mother (she looks about 65) transfer out of a wheelchair you would think nothing was wrong with her at all. And you would be right - for the first 100 yards of walking after which she would be out of commission for the day.
As others have said, all the WDW CMs are extremely helpful when it comes to meeting the needs of someone who is in a wheelchair or EVC, but the bus drivers are probably some of the hardest working and most caring people you will meet anywhere.
And congratulations on your anniversary! My wife and I spent a week at WDW for both our 35th and 40th. JUST US! No adult kids, no grandchildren, just us. We plan to do it again for our 45th in Jan. 2019. I hope you and your wife have as much fun as we did.