Thanks everyone for your help. The show was Wednesday night (virtual Friday where I live) and all-in-all the show was a huge success. The band played well and the audience enjoyed the show. Everyone in the band, and the manager and Darius' wife were all very gracious. A great experience.
I ended up using:
Piano: pair of Fatheads just inside the lid
Drums: pair of SM81's in X-Y
Bass: JDI on the send of an Eden head, Rode NT1a in front of the speaker
Sax: SM7b
About 25' of portable band shell behind the band.
4 separate monitor mixes
I brought my own setup, and just hooked into the theater's side surrounds with a 50ms delay and some EQ to help in the back of the room.
All they traveled with was a sax, drum sticks, and a few cynbals so I had to source the equipment and then spent most of the 1.5 hour sound check time readjusting the action on the bass, working on drum sounds, borrowing other snare drums from friends,...
I got great recordings and live sound from everything except the piano. The piano sounded OK live, probably because 1/2 the sound was acoustic (Yamaha C5 Conservatory). Using the Fatheads on piano was a mistake for a couple of reasons:
- I have never worked with them live
- The figure 8 pattern caused me grief: too much sax. The sax player set up in the front of the open lid and wanted his monitors at rock concert levels (a stand-in sax player for this brief 2-city tour), so the sax monitor went into the piano lid into the backs of the mics and was almost louder than the piano. The sax guy insisted the monitors be on his left (I guess he had a bad ear), so they essentially had to point up into the piano lid
I got some distortion from the Fatheads when Darius hit the keys hard. The preamp (ISA828) wasn't clipping (but was fairly hot) and I was well below digital level, I'm not sure yet what the problem was, I need to run some tests on the mics.
- I got some feedback during songs 3 & 4 in the first set after responding to a request from the sax player to turn up his monitors. At intermission I dropped the piano out of the sax monitor and moved the monitor a little to get more volume for the sax player, but in the second set the sax started over shadowing the piano in the Fatheads.
Please don't take this as me dishing the Fatheads, I accept the blame as an amateur.
I'm not sure if its possible, but the recording on the Fatheads sounds worse (more occasional distortion) later in the evening, after the feedback. I'm not sure if I damaged one of them.
In retrospect, I should have used the second pair of SM81s on the piano.
Well, it was my first jazz gig, and the band was either very polite or they really were happy with the sound. I'm pretty picky. The bass, drums and sax sound awesome on the recording.
Lessons learned:
Don't try new mics in an important show
Don't use figure 8's inside the lid when there is a monitor pointing in there
Uh, don't point a monitor in there, duh
Don't listen to the sax player when he sends me the 'backstage monitor runner' after the second song to say 'turn up the sax monitor'. Only respond to requests to turn something down

Make sure the star sounds great and screw the other players. I suspect Darius was a little whacked because he too was in front of the sax monitor. He never said anything, gracious man that he is.
Solo instruments during the show into headphones. Had I done this I
may have picked up the intermittent distortion on the piano. I usually use my phones briefly. They were laying next to the desk...
All in all it was a great experience with a gracious band, and a good education for me. I'll try to post some pictures later of the setup.
Thanks again to those who helped me,