Technically you can do anything you want. You're the grower so you're in charge! That's a lot of responsibility but it also means you're allowed to try stuff and see what works!
All joking aside, you really can do what you want. Your garage may not be ideal but it seems like the inside might not be ideal either.
I always dry in my tent. It delays my next grow by a week or so, but I grow organic, so that's just part of the time I'd be cooking the soil anyways.
When you dry in your tent, the moisture from the drying plants helps keep the RH up at appropriate levels. If the temp/RH aren't where you want them, you can add a humidifier, etc on the outside of the tent although I've never had to do that.
If I were in your situation, I'd be looking at what's easier to fix...warming up the garage or increasing RH inside. If you have a tent, increasing the RH shouldn't be that difficult due to all the plant matter that will be shedding moisture into the air.
Let us know what you decide!