If I were flying with a small child I would tell him long before we got to the airport about what to expect and explain to him it is for our own safety. Would then go through it with him as if I was the TSA inspector.
If they know ahead of time it will not be near as dramatic as people are making of it.
I'd rather my child feel safe flying because EVERYONE was throughly checked than to be scared to death someobody on the plane had a bomb stuck up their azz waiting to blow at any minute.