Believe me - after campaigning for 7 years to get one, there will be some very strict rules associated with it. The multiple child jumping on the trampoline thing won't be happening. When my youngest had in-home therapists, we were told by the Autism center to get one. DH opted for a bounce house instead. When that thing is set up, no more than 2 kids are allowed to be on it at a time. My kids have gotten pretty good at taking turns. When they go to friend's houses, they'll even come in and whisper to me "Mom... they have (instert # here) kids on that trampoline at the same time" and I just remind them they know what our rules are and they will play by our rules.
I remember about 25 yrs ago I was jumping on one, went wrong direction and wound up with my legs split between the side attachments between the frame and tramp. My toes grew an inch I swear. I almost had a split personality. Learned my lesson well.