Luckily we went last year to the Balloon Fiesta since it was cancelled this year. It was absolutely incredible to see that many different shapes and sizes of hot air balloons.
Not sure how things will change in the future but be sure to check out their website.
balloonfiesta.com/
The balloon field is accessible with blacktop walkways around the perimeter as well as a couple through the center of the field. There are accessible bathrooms as well as powered scooters available for rent if needed.
Accessible parking areas are located in several locations but I did receive a special permit specific to the balloon fiesta which was able to be scanned at the gate. I just had to send a picture of my placard to their e-mail address with my name and address in order for them to mail it.