If you look on the Balloon Fiesta site you'll see that reservations for staying on the site itself will begin the day after this year's closing. They fill up fast so plan your dates around it. The area RV parks jack their prices way up for the Fiesta and you'd have terrible traffic to get into the Fiesta. I'd highly recommend you stay at the Fiesta site. We stayed 10 nights in the boondocking area and the free shuttle came by every 15 minutes. We also volunteered to crew a balloon which was an awesome experience and gave us a free long ride.
For the Grand Canyon, stay at Trailer Village RV in the park. You'd be right at the rim.
Same goes for the Utah national parks. Move to each one and stay IN the parks themselves for the best experience and a lot less driving and time involved rather than trying to see them all for one base.
Sounds like a nice trip. Have fun planning!