My overall point, though, is that it is easy to imagine a horrible, negative effect on a child's psyche, but it is more likely not a problem. Humans, and kids in particular, are fairly robust and adaptable creatures.

In my experience, for most fears about X people have, X alone usually is not damaging. However, being surrounded by people who are convinced X is bad will make it more likely that the person will believe it. This tends to cause more issues than X does.

If a kid has parents and other close people around him/her who believe wearing a mask and not seeing people's faces often is bad for the kid - then it will be.