Premier Gymnastics Certificate for a Free Birthday Party up to 12 Children. Ages 3 - 18 use the Main gym, Up to age 6 have access to the Preschool gym. Additional Children beyond 12 are $10 per child. Every child must have an online waiver to participate. Parties are 90 minutes and include 30 minutes in the party room and 60 minutes in the gym. Gym includes foam pits, bouncing on trampolines, games, and playtime in giant inflatable. Only those 3 years or older will be allowed in the gym. Must present certificate to book the party.