When loaded, the voltage will drop some (not that the circuit in question draws all that much current when the relay is not energized).
The IC CMOS4001 can handle up to 18V (absolute maximum, not for regular use though).
A 12V relay won't like 17V for a very long time, but if you have the relay, mount the diode (D3) directly on the relay terminals and use the relay for a load while you measure the voltage - a few seconds won't kill it.
Or, you could load the supply with a 12V lamp of an appropriate wattage and take the measure.
Post the measurement here for added help.