T.B.
We have a four yr old and almost 2 yr old and our kids love the trampoline. The more kids you have jumping at the same time, the more chance that someone could get hurt, but if you watch them closely, I think they are great. Kids do better with only a few at a time on there, and with kids approximately they same size. A bigger kid can really launch a little kid accidentally, so we let our four yr old get on with just his sister when no one is over, but we don't let her on there with him if he is up there with his friends. You need to teach them basic safety things at first, we tell our son not to bounce right next to his sister etc. and he knows if he doesn't follow the rules he won't be allowed to jump. When you get too many kids, the chances of head collisions and other bumps is greater, so depending on the size of the trampoline you get, limit the number of kids on there at once. With just one kid at a time, I think they are really safe, with every kid you add, you increase the chance for injury. My husband and I even get up there with the kids. It is great exercise, but it is hard not to be sent flying if you catch someone else's bounce. If you are going to have different age groups at the party, I would recommend a timer, so you can give the older kids five minutes, then the younger kids 5 minutes etc. That way, they know when the timer goes off it is time to get down etc. Definitely get an enclosure, and make sure they actually zip it while they are in it. We have had ours for two years now, it gets used year round and we love it. My kids ask to jump almost every day and I like that they are getting all that exercise. Just a safety note, we keep a lock on ours so the kids can't get on it without permission (and it also keeps any neighbors kids from trying it out when we aren't home)