The kids looked old enough to make this decision on their own.
I hope this is the start of a flood of people peacefully bearing cups and bottles of water being arrested. (See Ghandi)
I see nothing wrong with bringing children of this age into it. Maybe I am wrong. As long as the parents have taught them to act respectful and peaceful, and obviously, these children did.
It is difficult to believe that the parents did not sanction this. But, then again, what does it matter if they did.