This is just a "gut" feeling, but for BOTH your sakes, I'd seriously think about a wall A/C unit. The temperature inside an enclosed garage is much hotter. If any planes are made of balsa, the heat can't be good for it. I think the airframe would "age" and become more brittle quicker. I'm not sure about radios and engines, but I wouldn't feel good about it. Besides, would want to be comfortable working in there don't you?

Duane