I think you are very careful with your choices. I bet your husband realized that maybe that adventure was just not the best choice.
My husband and I were married for 10 years before we had our daughter. We loved going to movies, book stores, really nice restaurants. Once I realized I was pregnant, we started appreciating the things we would not be able to do for a while, if our daughter was with us.
We gladly put off these things until she was old enough to understand, to use inside voices and to use her words.
Instead we enjoyed a lot more "outdoor fairs" , Renting a lot more DVD's, Eating at more family friendly venues, And making sure our daughter was able to stay on her schedule to have the best results. And we only had 1 child.. so I can imagine with 2 it is double the excitement for you guys..
You did your best in that situation, who could have known the kids would become frightened? You did not plan this, just learn from it and move on.. The woman, needed to up her medication and calm down.
I will now wish a curse on her. "May her privates become inflamed and weepy."
I try to not become irritated by these situations, but if the parent just sits there and ignores the child, I am not pleased, but sounds like you were trying to calm the children down.
I honestly have actually asked if the parents would like for me to help them find the item in the bag or stroller they are searching for. I calmly tell them "it is ok, that everything is going to be all right".