As a parent, let me be the first to apologize to you. The same thing has happened to me, and I was not nearly as nice, I screamed STOP. Then I proceeded to give a lecture to the kids, and never did let them pet my dogs. The result, a parent came up to me and said all snotty "If those dogs aren't safe, then they shouldn't be out on the street."
I told her "Walk on --tch, my dogs are fine, your *u*k*ng KIDS need to be on leashes." Like you, I don't mind if a couple of kids walk calmly up, but a screaming horde of children makes my dogs nervous, and nervous dogs are unpredictable.
Stella
Edited for spelling-lol