After Los Angeles County put a ban on trick-or-treating for 2020 before walking that back a bit, Eater SF asked San Francisco health officials about how the ciy would handle Halloween this year.
The answer? There's no plan to ban trick-or-treating, but they do strongly discourage it and urge parents to keep children home on October 31st. Noting that the sharing food, candy, and items is dangerous in a COVID-19 world and that maintaining six feet of distance with families gathering on streets is also difficult they prefer individuals don't partake in that behavior.
They suggest decorating as you usually would and wearing a face covering under your mask. Perhaps you could also enjoy this year's Halloween full moon in a socially-distant setting.