I was shocked watching the programme, not least because the children of the group were obviously as much "victims" of it as the poor bereaved families that they were picketing. Also, I'm amazed that someone somewhere in the area that this group live hasn't reported them to Child Services when they are taking children out on the streets in full knowledge that they will be at risk of attack and injury - shown vividly by the poor little boy being hit by the drinks carton. Surely this is at best neglect, and at worse, a deliberate intent to put a child in danger.
My own view would be that any demonstration, whether political or religious, should only be attended by adults. My reasoning? Simple. You have to be 18 (in the UK at least) to vote, therefore I think you should be 18 or older to attend a political demonstration. (I'm ducking now folks, since I reckon a few will disagree with me on that one)
As far as religion is concerned my view would be that until a child has reached "adult status" (I know that age varies in different countries), then you should have to be that age or older in order to demonstrate. It would save children being used (or is that really abused?) in order to create additional numbers/shock value or whatever when these demonstrations are held.