Is it ok to power several op amps with the same pair of 9V cells?
Yes. In general all the circuitry on a board that uses the same voltage has the same supply. The only exception is when you have (for example) "digital" 5 V that will have noise on it and "analog" 5 V that is cleaner.

I am assuming that the batteries can supply enough current to power your several op-amps. 25 mA is fine. Higher currents will result lower mAh.