Pavel, thanks again for pointing out that the outputs on the IO expander were sinking outputs. While I had looked at the TI data sheet, this was not clear to me.
Your solution worked just fine and everything is working as it should.
In the ‘as shipped’ configuration, the IO expander is set up for 3.3V operation and that works just fine with a 5V relay board. I still have to decide if I want to operate that way or if I want to set up the IO expander for 5V outputs to drive the relay board that way.