I don't think you were snotty at all, limey--mom should have appreciated your attention and pleasant tone, if she wasn't going to watch her child closely herself. Shops can be dangerous for little kids whose parents let them do whatever they want.
We had a small child in our store who was shaking a rack, while his parent stood right next to him doing nothing to stop him. The rack was coming loose, so out of alarm I said sharply, "DON'T do that!" I think I scared both of them, but that was a lot better than having a hurt kid on our hands.
