So things worked out really well....the Curbside checkin with skycaps and everything was very quiet and we got one to help us do checkin as soon as I pulled up to the very beginning of the T4 building. He checked us both in while the rental car sat at the curb for 3-4 minutes, and then I was able to return the car (and even had enough time to refuel it) and take the Skytrain back to the terminal where mother waited.
A well deserved gratuity was provided of course ;-)
But the other options mentioned were definitely in the back of my mind the whole time....of course the JFK-SFO flight is delayed by about an hour today...but that's not a big deal right now...