Oh goodness! Pixies for you to feel better
As far as advice goes, I'm fairly limited. I can safely say you will get assistance at the airport....when I went to Disney in August there were several Logan employees pushing hurt and elderly individuals onto and off of the planes - and around the airport. Disney will also be very accommodating I'm sure. I would worry most about the parks, but if you are traveling with a friend who will make sure not to push you off a cliff you'll be all set! When I went with my grandmother a few years back she rented the motorized vehicle thing, which was fantastic because she couldn't have walked around the parks all day. The issue with those vehicles is the absence of a brake! Which, with an 80 something year old, turned to be troublesome. I got ran over a couple times because I went in front of her to make sure she didn't run over a couple kids (did I mention how heavy those are when they run over your foot?!)....but in general I don't think you would have any issues renting one of those and having a drink or two.
I have only canceled one trip in my life (there was a death in the family) and I tend to brave all circumstances! I even broke my foot the day before going to Hampton Beach but went anyway.....crutches and sand are not a good combination
! So if I were you I wouldn't cancel, but only you know what the best decision is. I think Disney/airports have these type of situations on a daily basis...they are well equipped with handling these issues.....I really wouldn't worry about them. Good luck with everything!