‘The child had to eat something’ you say...was the kid on the verge of death and needed food immediately? It was a grocery store, for heaven’s sake. If the kid ‘had’ to eat something, there was surely something in that store he could eat that would have been safe.
I know people whose children have nut allergies, and they do not rely on total strangers to know what is best for their children. Usually if they are in doubt, they don’t let their child consume a particular food. It’s called common sense and responsibility.
Since you're a devout Catholic, pray that we may learn the cause and cure for this dangerous health problem. Many miracles have happened in our understanding of disease. We need this one.