So each "motor" in this case electromagnet will get 11.1V or will it divide because I have 3 running at any given time?
Each "motor" gets slightly less than the voltage that you are supplying to the motor driver.
Should I possibly get a 7.4V battery instead?
You can use any voltage you want, within the restrictions for the motor driver.
Im not sure how many turns or wire length that could fit.
Wind the coil and see.