I'd agree on the 570. Enough power to keep them entertained but not so much that a loss off good sense, which happens at that age, will kill'em. Fernando had one and he wheeled it pretty hard with little trouble. I got the impression that the drivetrain and axles are tough enough for whatever abuse the engine could deliver, which is good for kids and the parents that have to fix it. A RZR800 could be a good choice too. I really like the CanAm Maverick lately but there's a lot to handle for a teenager there. Ultimately they're counting on you to make the right choice for them, which you can't, because they're teenagers and parents are dumb and mean. HAHA