I'm not trying to sound like a badass navy seal or anything here, but if I saw 3 kids coming at me with guns, I wouldn't be assuming they wanted to steal my truck. Having the advantage of concealment and all three pieces of shit in a few degree target area, I think I would have emptied a magazine in their direction and taken off running in the other.
That's just me though. I've seen countless videos of young scumbags like this. As soon as a gunshot goes off, they scatter like the cockroaches they are. They are not expecting confrontation. They assume they will have an easy target.
There is no right way to act though. Everyone has a different level of acceptable compliance.
Once they are around you, though, they have control of the situation.