While I agree that it's impossible to guarantee that you will or will not get brownouts, I'm going to go out on a limb here and say that it's a significant risk. If you plan on running these mechanisms at the same time, you should probably add some code that checks and regulates current draw.
You can also learn more about designing with motors and current draw
here
Cim motor curve:
http://motors.vex.com/cim-motor
And mini Cim motor curve :
http://motors.vex.com/mini-cim-motor