We bought the Skywalker Elite 15 ft trampoline with enclosure for our daughter's 9th birthday. She loved it and still does months later. I was a little hesitant about buying a trampoline, but it seems really safe with the enclosure (well, as safe as a trampoline can get anyways). I always watch my kids when they are on it and only let one on at a time (they LOVE this rule...haha).
The frame is very study, my husband had no trouble putting it together (took him less than 30 minutes). It has wheels on it so that when my husband mows the grass, it's really easy to move around in the back yard. It does take up a lot of space, so I would recommend buying a smaller one if you don't have a lot of space... your kids will still be happy.