What a great experience! I have had the good fortune to hang with Oteil a number of times. Back in the early 90s my old band did a number of gigs with the Aquarium Rescue Unit, so there were various sit ins back and forth. I think that band perhaps showcased his abilities the best, with Jeff Sipe and Jimmy Herring pushing him on and Col. Bruce overseeing the mayhem, he was inspired to do things that aren't really appropriate in his later bands. Since then, we've crossed paths a few times, most recently when Great American Taxi opened for Bill Kreutzman's band here in Colorado for a couple of shows.
I think you got the best part to play. One of the reasons I think that Oteil is one of the foremost bass players out there is his harmonic sensibility. If you had a chance to discuss chord tones and tensions with him, I'm sure you learned a huge amount! His reharmonization of Amazing Grace on Rising Low is just wonderful.
And, as you say, Oteil is not just a great player, but a wonderful human being!