I'm in a similar situation but for, the air compressor kicking on will remind them where I am at
Just kidding.
I looked at the drawings you attached and although being so new at this I do not have a lot to add but being in the electrical business for my entire career and relating electrical flow to that of fluid or air, the only concern I would have with the one regulator set up would be the relationship both nozzles will have to each other when you are adjusting flow. I don't think it will be a game stopper but when adjusting one you will ultimately adjust the other.
For instance, if you have 10 psi and you are dividing it equally between coolant and air and then you adjust the coolant to 4 psi, your air will increase to 6 psi. this could create difficulties in getting that fine tune you are looking for.
Other than that, it looks great.