I got sober in October of 1981 and dreaded the approaching holidays! On Halloween I thought everyone else in the world was drinking, and that drove me to my first AA meeting, when I'd already been dry for a couple weeks.
In my experience, "No, thank you" is usually all I need. People other than myself are just not paying very much attention to who's drinking what. If pressed, "I'm driving" or "I'm on medication" are enough, and if asked about what medication, "I'd rather not discuss it."
Giving beer to parents of trick or treaters sounds just bizarre. "I don't drink around the kids" is true enough, since you don't drink without them either.
Anyone who tries to pressure you after you politely declined alcohol has a problem with etiquette, alcohol, or both. Happy holidays!