Lots of kids were wearing a new mask for Halloween: a COVID-19 mask. There is one poster to the Daily Photo site who is opposed to mask wearing. This may come a surprise but he has a point. Most folk agree masks are a barrier to transferring the COVID-19 virus from one person to another but there are some caveats.
Masks must be clean. And masks must be dry. Masks should not be quite damp, saturated with contaminated moisture from one's breath. Google this. You may be surprised to learn that moisture retention in reusable masks may result in poor filtration and, and this is the big surprise, increased risk of infection.
That said, the child pictured is wearing a clean, dry mask. She is at the door but still outside. And we, my wife and I, are both wearing fresh masks. We wore gloves to place candy in bags and we used tongs to give the bags to the trick-and-treaters. We believe our handing out of Halloween treats was a low-risk activity as far a spreading COVID-19 is concerned.
For more info on mask wearing, check out this post by the ECDC (European Centre for Disease Prevention and Control.) Scroll down to number 5, It is clearly stated that the appropriate and consistent use of face masks is key for effectiveness.