How do proportion current for components?
If you use a resistor divider to regulate the voltage you are going to waste energy as heat through the resistor. Another problem that TEC control presents is the load is dependent on the temperature across the device. So simply limiting the current or voltage will not give you a stable temperature. A better way is to use a DC to DC or voltage regulator to control the energy into the peltier. 

A thermal sensor is needed to control the peltier. The modules can sink up to ~60W of energy and 6.4Amps max with the voltage being no more than 16V. 

With two modules you'll need around 120W of power and a 15V (or 16V) supply. I suppose you could go with 12V to match the fans (and another 10W) but you'll limit your power. 

Here is a great article on peltier control.  This is just an example, there are other controllers and some don't require a microprocessor for thermal monitoring. 

If you do not insulate the box of your 'mini fridge' adequately  the peltiers will not be able to pump heat out of the box fast enough and the temperature will not drop.