Either way-if your main AC is a heat pump I'd match it and put a unit back there.
Honestly-whether it will fulfill your needs is debatable:
The heat pumps work well when it's cool but not freezing-I find that even though my unit will make heat at 35 the heat blowing from up high does not make it comfortable sitting in the recliner-and when it shuts of you feel the missing heat right away-I need heat at the floor to make the unit nice to stay in(ceiling is high in the fiver) Now, in the garage that may not matter-if you're just using it to sleep-or for storage whatever heat you can get in should work for you.
Also-can't you manage your plugs to keep the heaters on and still make coffee? Usually with a 50A unit you have enough outlets to run 2 space heaters and have a kitchen outlet still on an unused circuit?
And-Does the CG pedestal have an extra 20A plug you can run an ext cord from to you garage? or a 30A outlet you could reduce down and use for extra power?