Thank you. Cost is not an issue for this prototype. It may be when I start producing a quantity. But perhaps Option 2 is my best first option. I am not being successful at inserting an image of the circuit that I am using into this post, but it is similar to the one that you inserted. It is a discreet low-side circuit with an N-channel MOSFET (see,
http://www.precisionmicrodrives.com/application-notes-technical-guides/application-bulletins/ab-001-discrete-driver-circuits-for-vibration-motors).
So, I am not quite clear how your sketch corresponds to the PCA9685 outputs. Am I correct that the board has 3 outputs for each motor (PWM, voltage out, and ground)? Would this work using my circuit? In this case, each PWM output from the PCA9685 would feed into one of the MOSFETs, and each voltage out and ground from the PCA9685 would connect to one of the ERM's anode and cathode. Correct? BTW, the ERMs are rated at 75mA at 3V.
Possible or is this board not the right option?