Peltier cooler circuitry

What's the Voltage rating of the modules, and do you figure you'll require temperature control? (I guess the need would depend on the size & the insulation of the fridge.)

 

Ok, with that space, insulation & power it's quite appropriate with a temperature control. Is your uC output linear, some fast PWM, or simply a slow on/off?
I'll point out that Peltier's will be more efficient when driven with a constant voltage than if turned on & off. During the off period they'll "leak the cold out" of the fridge.
On the other hand a simple linear drive will waste a lot of Ah's as heat, so a linear uC output driving a switch-mode "inverter" then driving the Peltier is by far the best option.

 

There are some quite simple power switcher IC's available. You need only the IC, maybe a transistor, an inductor, a diode, and a couple of capacitors & resistors.
There are of course some design (& layout) rules to observe when it comes to high frequency, high power circuits, but it's not really too complicated to make it work.
Is that 6A @ 15V for each of the two Peltier's, adding up to 12A max? Will you design & produce the PCB's yourself?

 

You'd need to design the inverter for a hefty 12A anyway then.. Is it an important feature of the fridge design to have that much spare cooling capacity?
Many of the IC manufacturers have an evaluation PCB layout for some of their IC's. They usually also state some basic layout rules in some of their documents.
I can guide you if you don't find sufficient info there, but my capability to help will be quite limited from the weekend and two weeks forward as I'm away on vacation then.