I would still measure the solenoid voltage, or better yet just use the Self-Test while all the solenoid outputs are enabled and see if the 24V rail dips at all. Should be a quick test, just nav to the roboRIO webpage and press Self-Test after selecting the PCM. If the voltage rail doesn't dip as a result of turning them on then you should be good to go.
Self-Test button is explained here...
http://wpilib.screenstepslive.com/s/...ribution-panel