Did you see where the credentials were from? Is it possible they were just her work place identification? Since she didn't look at you and got back in her car I wouldn't worry about it.....besides what do you have to be worried about? You are in ratio, the kids were playing outside, you were supervising the kids closely and the kids appeared well. Everyone knows kids cry, it just sounds so much louder outside!!!
Maybe a neighbor did complain, but oh well, if this woman was checking you out and found something wrong she would not have driven away.
Have a glass of wine and a good night.........and don't worry