Hi DC,
For the reference IC, I would recommend ADR435 which has an output voltage of 5V, output accuracy of +/- 2mV (B grade) and a temperature coefficient of 3ppm/C. It has a wide operating range (7V to 18V) and would suit your design perfectly as you are using 10V supply.The ADR435 has the capability to source up to 30 mA of output current.
I have suggested the ADR435 in the assumption that the opto-couplers (one opto-coupler per digital line) that you are going to use in the design will have around 5mA of current consumption. If you would like for your system to have lower power consumption, I would recommend looking into ADI's digital isolator portfolio (i.e. ADUM2400, at 5V operating supply, has 1.0 mA per channel maximum up to 2 Mbps).
Regards,
Mark