Hi, Birthday parties at gyms are big here . . .
We've been to a lot - at different gyms - at different ages . . .
Most operate like the gyms typical recreational class
then they add something like a blow up, dance games (similar to what you would see a DJ do at a block party), parachute (for younger age set ), birthday kid gets to "fly" if the gym has a harness
They usually run 2 hours.
1.5 hours in the gym and the last .5 hour in a party room for pizza & cake. Never been to a party where the kids go back in after eating (no surprise there LOL)
Costs are based on 15 kids + birthday kid. additional kids cost ya anywhere between 10 - 15 bucks (I think one place actually asked for more!) For how much to charge . . . you should place some discreet calls to other party places (not just gyms) in your area . . . get an idea of what your area expects to pay
Does that help?
oh ages! . . . been to one as young as 2 and as old as 10