Thanks . . . funny you should mention a 120 vac relay
I did some more nosing around on the web and came to the same conclusion, a 120 vac relay is the way to go . . . but where to find one? (I live in a rural location in Northern California) . . . so sticking with my original plan, I went to the local Kragens looking for a 12vc SPST relay . . . and while there met a guy who jumped in with a "Why don't you try WAPCO on Jacobs? . . . they got all kinds of stuff" (I am very partial to "stuff") . . . took a bit to find it, but what a treat, all kinds of "stuff" . . . and a very nice 120 vac SPST relay with mount for $10 (I think he said rated for 5 amps, more than enough, and voltage independent)
So, now to put it altogether over the weekend and let you all know how it works (or don't).
You realize, of course, that this is one of the "dreams come true" for folks with backyard flocks . . . to be able to have the flock in and out without having to depend on neighbors (who are very happy to handle the feeding and watering for the eggs . . . but 6:30 AM (or earlier) to open the coop . . . and then making sure it is closed . . . well, that is pushing "neighborliness" a bit when you start talking about 10 or 15 days)
. . . . anyway, will get back to you as to how it goes, but it looks good from here.
D