Thanks again for the advice, folks.
Regarding liability insurance, any recommendations on where to buy it cheaply and efficiently (perhaps online)? Or a ballpark estimate of how much it should cost? Can it be used just for a single event or is it applied over a period of time to cover multiple events/continued usage?
I continue to lean toward the generator route — we are in the Northeast US so with all the hurricanes we've seen in recent years there's a good chance someone in the neighborhood will have a portable one that suits. I'm also going to work on adding up all the current draws of our amps, mixer and speakers (thanks for the clarification about pedals, Mike). But I also have been reading on other forums that using very heavy-duty extension cords from a single wall outlet or outdoor GFCI outlet (or perhaps two outlets) can successfully run a small rig like mine. And a couple of weeks ago I ran the same equipment in a small Knights of Columbus hall using only the wall outlets on and near the stage, in combination with my two Furman 6-outlet conditioners. I don't know much at all about 20-amp circuits or whether all of those outlets were on the same circuit or not, but we had no noise issues with the equipment and no power interruption issues either. Additionally, none of the other forums I've researched are dedicated to AC power and grounding like this one is, and I know you all are experts there whereas the other forums (places like Gearslutz) are generalists. But I guess in light of the aforementioned factors I'm still wondering whether, if all our equipment uses "grounded" power cords and balanced connections for mics and speakers, the one-or-two-wall-outlets-fed-by-heavy-duty-extension-cords method will truly be unsafe.
Really appreciate everyone's time and attention to my newbie/novice problem. Thanks again.