There's a preschool near me that I walk by every day. Their playground is constantly full of 3-4 year old kids, all of whom are properly wearing masks. In other words, you have worse coping skills than a toddler.
Ding ding... schools here are filled with kids wearing masks. One can argue it is not useful, but that is not the point at all. The point is, they wear them without complaint, every day. Hell, my kid has her mask on before we walk out the door. I tell her she doesn't need it, but it's just easier for her to put it on and forget about it than remember to put it on when we get where we're going. She's a picky kid with sensory issues, so...
I see the height schoolers wearing them when they are across the street at the mall. If high schoolers, the most likely to rebel, can do it, anyone can.
There is absolutely no way that 3-4 year olds are consistently wearing masks properly unless there is like 1 teacher per kid fixing their masks anytime it moves.
Please don't say "in Europe". Diseases are often driven by schools and kids of all ages, in my country the expert commission has been asking masks for all kids at school, all ages, for a while now (they generally have plenty of evidence, but I don't read too much into public policy), but politics have not implemented these requested changes, probably for fear of backlash.
There are many countries in Europe and they differ greatly
As Epse says, there is no “in Europe” for this. The rules for masks on children varies greatly between countries. But letting the kids wear a mask is certainly not seen as child abuse over where I live. Maybe as unnecessary or as “overly cautious/protective” but I haven’t heard of people calling CPS because children had to wear a face mask.