MOSFET output I on Arduino
Peltiers can be hard to figure out how much current they will draw because it is dependent on the temperature across the module. You could hook it directly up to the a power supply running at the same voltage as the supply rail to your mosfet, then check the current while your swinging the peltier module across the maximum temperatures that it will experience in operation. Then take the max current figure and make sure that is lower than the rated current of your mosfet. If your worried about the current then start with a lower supply current then ramp it up later when your confident the circuit is working. I would not parallel the peliters, but put them in series as you probably don't have matched modules and the mismatch could send much more current through the other module.