It's alright for the parents to do this; they're adults and they know what's going to happen. Even if the kids asked their parents if it was alright for them to take part, the parents should have said no. Now these kids will be subject to the indignities of police custody and all that entails so that a few protesters can get a photo op designed to tug at the heart strings.
Think rationally, people. Would you want your kids to go through what those kids are going to go through if you could stop it?