Geeze, you guys are some cranky bast.... Well, yall have some valid points on both sides. Kids are inherently curious about cool toys, and will come running at the very hint of one being played with. Deal with it. The worst thing people can do is portray our hobby in a bad light. Being cranky and grouchy is just that way. It's alot easier to tell the kids that it's not a toy, and can be dangerous. If they persist, ask them how they would feel if they hurt someone with your gear. Offer to let them watch, but tell them to stay in one spot so noone gets hurt. And put a show on for them.
If you tell them to piss off and go away, they just might, and they just might tell their parents about the mean guy that told them to piss off. Then the parents might get the wrong impression and do something about the mean people telling their kids to piss off. See where this is going? Think you're safe?
Take a look in my gallery. Find the pic of the helicopter. The field in the background is a public park. I always respected the non-rc people in that park, and talked to passers by and tried to keep the PR high. Some guys that flew there thought it was funny to buzz these same people with their helis and giant scale planes. Well, those pedestrians got together and got the county to OUTLAW any type of R/C aircraft in that park for safety and noise reasons. It didn't matter if it was a glider, park flyer electric, or a big giant scale. A damned shame since the field was huge and dead flat. A perfect place to fly, but no more. Fly your stuff and get caught, they take your stuff, fine you, and then you have to go to court. I'm not BS'n, it happened.
True, kids can be a pain, but if you give them the impression that you are involving them in the activity, then they will stay in line. Another possibility if you have a computer radio, is to dial back the throttle ATV so that they can drive it, but it won't go past 1/4 or 1/3 throttle. Tell them that you set it like that so they won't hurt anyone, or damage your stuff. There's always solutions.