Huge thanks!
Thanks to mojocat , mpuzzle , mavrik1033 , kraftwerk2020 , dawny_darko , janezy , and tenandtonic for their help this weekend! (And to notbatman for driving over to let me back in my house after the screen door got latched during cleanup on Saturday).
We have footings! We went from thinking a week ago it was either a hire-out job (i.e. bring in a bobcat) or avoid digging (probably wouldn't have met code and would have been a bad idea) to having it done.
I don't think any of us started Sunday thinking we'd finish that day, but with an exceptional extra effort from Mojo and Mpuzzle, we finished up at about 8:30PM -- in the dark, but thankfully not rain/snow.
Hope for having the deck in this fall (and thus easy access to the hottub through winter) is still alive!