You have 2 options for your mode of transportation.
1- Try your luck at parking in Uptown 
2- Use the free shuttle service
Shuttle parking and pick up will be located at Posse Grounds Park & Ride Lot
(20 Carruth Dr) & West Sedona School.
Shuttle service will begin at 4pm departing from the Posse Grounds Park & Ride Lot, 
People will be dropped off at 431 Forest Rd (which shouldn’t be longer than a 10 minute walk to destination)

Location of the actual Thriller Flash Mob will be:
Sinagua Plaza 
Times:
6, 6:30, 7, 7:30, 8.

Practice at Home with this Youtube Video: