So, to clarify, freezers will be okay in sub-zero temps, but refrigerators and refrigerator/freezers won't operate correctly?
Correct. If nothing else - you mentioned your father stores beer in the fridge. In the middle of winter(at least in my area), the fridge won't operate at all, but the contents will still freeze. Not a good thing for a fridge section. A true 'Garage Fridge' is more of a 'Climate Control System'. Seperate systems for the freezer/refridgeration unit, including the capability of heating to maintain the temperature above freezing in the fridge section.
Above ~40 - operate as normal, if not in an area with AC, 120F+, heavy duty AC unit might be good.
~40-32 - you need seperate cooling for the freezer and fridge sections. Otherwise the fridge freezes... Electric heating strips would also work, but be inefficient.
1-32 - Still need a circuit for the freezer, heater for the fridge section
Below 0 - need a heater for the fridge. Freezer won't turn on.
My freezer has a heating element to heat the compressor to operating temperature if necessary, so between ~0-32F it actually uses MORE electricity than at slightly higher temps. But it still runs less often, so I figure the energy use remains about constant, my food remains cold, and I'm happy. I have a fairly large unit, so keeping it in the garage is a big space saver. It's out of the sun and rain. I DO have it elevated a couple inches just in case of flood.
If you expect it to experience freezing temperatures a lot, I'd check the manuals to make sure it's got the compressor heater - many of the cheap chinese ones don't, and they'll specify not for use below freezing. Mine only says that for best efficiency it's best to keep it out of freezing temperatures - 'Energy usage may increase' or something.
BTW, I'm in North Dakota, so it gets even colder than Charby's.