A quick update: there were two great events tonight, both of which I only encountered on the periphery: the aforementioned Halloween Party at the Dean North/Walt L. Shamel (the name those who run it use) Community Garden, and a scavenger hunt through local businesses that started at Bristen's Eatery at 8 pm. The latter was aimed at adults, as I found out from Bristen herself when I cracked a joke about being too old for it on my way to the subway. Had I known, I'd have stuck around.
The "Know Your Audience" Award for most enterprising costume goes to the kid I saw dressed in a suit with a Barack Obama mask. He'll be eating candy until Memorial Day.