ak, I would have to disagree with your second paragraph. Parallelling inverters is a common way to increase output. I have used such a circuit to control a small dc motor for years without a problem. The circuit looks clean on a scope and most likely a single pair of inverters could drive the motor if they only run at 4 ma. I do agree the CD40106 would be a better choice, I didn't have one on hand to breadboard so went with the 4069 to test.