I would have done the same thing. In fact, I would have made so much noise about it that the store clerk probably would have asked me to leave!
[I like the purple "EEK" guy also, Bill!! He's one of the funniest].
Anyway, I have this thing about Children being in a possible harm position. It makes me a little crazy and somewhat vocal, instead of passive. My friends feel the same way. Most of them are very tough looking individuals, that appear "hard core" on the outside, but when an issue where Children get harmed in some way comes up, that's when you really see inside of them.
Guess that the lady didn't even realize just how fast someone with a horrible fetish, or just a screw loose, could have taken off with those kids. When I read your message, I teared up thinking about it.