I don't know, If that is the rules, that you pat down a person when you place them under arrest, then so be it. Age doesn't matter. It is what they are instructed to do in the line of duty.
If not some big shot lawyer would tear them apart if they did something wrong.
If those kids had something on them that could hurt not only an officer but themselves then they must know what they are dealing with. Maybe the kid had a back brace or something, who knows.
Hey, who would have ever thought that a 4 year old would take a gun to day care, but he did. I am not saying that these kids were armed, But I do know that if I was taking charge of two kids I would be making sure of what they had or didn't have while in my charge.
By the way you are right about those parents. They were report as saying that they were very proud of their kids.