What are your qualification for the position
I have every qualification as a parent. I through experience know things happen but you do your best to control them. There is NO WAY a three year old kid should be running around, walking around or five feet from his mother....Period. That is what carts are for and if the kid was too fat for the seated part than the huge buggy would have worked just fine.
How do you assume that the child was wandering anywhere? Five feet is far from wandering. The mother could have simply been letting the child walk.
Your arrogance certainly comes through with your comment about the child being too fat for a shopping cart. Was the child fat or is that just a red herring on your part to defame the mother as a parent?
If the opportunity to let a child walk is available, instead of riding in a cart, walking wins out every time. Walking allows the child to receive some exercise though it may require you as a parent to expend some physical and mental energy that you would rather not expend.