You don't come out and say you were afraid (only uncomfortable), and maybe this is because you weren't, but I would have been. Since the two youths had no intention to order, my mind would have been going to what their intention was, and mayhem would have seemed a real possibility. I'm glad that didn't happen.
So to answer your question "what would you have done," my answer is, "leave, proactively." I would have recognized that this was perhaps an overreaction, but nevertheless a prudent one (in my judgment) for my family's safety. Confronting the troublemakers would have held too much potential for escalation beyond my ability to master. Doing nothing would have made us sitting ducks if real trouble broke out. Just making sure my family and I
weren't there when the trouble broke out would have posed itself to me as the best response. I would have considered the possibility that I looked like a coward in my children's eyes (and I wouldn't like that), but on the other hand I would have been sending them a lesson about self-protection that might stand them in very good stead in some future scenario.
Then, once we were safely out of and away from the place, I would have called 911. The police who showed up could evaluate the right response to the teens. I would have considered that my responsibility to the patrons, employees, and Gus, rather than to leave them all victims to whatever the teens decided to do next. If the police decided the teens were harmless mischiefmakers and a "be on your way" was all that was required, so much the better.