Being proud to be "obedient" is not always a good thing. Also this cannot be generalized. Plus it doesn't make something being mandatory right, especially when looking at people's smiles is crucial for kids development.

What I'm observing is that peculiar mix of self consciousness, smugness, and pride you sometimes see in young children, when they believe they are acting morally.

I'm not using quite the right words here - the emotions I'm listing are more mature. But the same emotions exist in children, just not fully matured.

Since the parents were maskless, I think the kids wanted to wear theirs because they've been taught at school that it's the right thing to do. The ones I observed appeared to be around eight years old.