Well, I've certainly done it now--Husband has politely suggested that I move the finches into the garage. I think he may have finally hit his tolerance level for broken squeaky toy songs from the zebras

So attached is a not to scale drawing of my garage for those who might be interested.
I'm facing a few complications and I'm hoping some members may endow me with knowledge so I can make this transition happen. Otherwise I may walk into the office/bird room to find that someone has "accidentally" set the cats loose to end the squeaky toy menace.
I live in Arizona. During the summer time, it's not uncommon for the temperatures to reach 110°F/43°C and higher. I haven't ever gotten a thermometer out, but I think at it's peak the garage was 95°F/35°C during the summer, meanwhile during the winter time it dips easily to the high fifties (14°C round about).
Beneath the spoiler text is just me being overly wordy and explaining things, after the spoiler text is the main issue.
► Show Spoiler
The initial work that has to be done before the birds can be moved out to the garage is I need to install weather stripping so I'm not leaking hot and cold air willy nilly. The gap between the wall and the garage door is a 1/2'' thick in some places. The second step is to blow new insulation into the attic, which will be done some time in February. I'm hoping once this is done, the temperatures in the garage will be more stable.
Next is finding a way to regulate the temperature to something the finches are comfortable with. I'm not really willing to rent a masonry saw to cut a hole into the brick and then build a frame into the window for the purpose of installing a window AC unit--especially not when the previous owner of my home already cut two vent holes into the exterior of the south wall for a portable AC unit!
That said, my plan is to purchase a portable AC/heater unit to keep the temperatures more even in the garage, but this gives me two issues:
1) where do I put the bird cages+breeding cabinets to keep them away from any drafts created by the portable AC? The portable AC unit has to go in the south/south west corner on the floor because of the vent access. Would it be best to move the birds to the north wall?
2) Most of the portable AC units I've been looking at online have an evaporative cooling method, which is bad. I was having problems with my owl finch pair's eggs (three clutches and not a single fertile egg). I'm suspicious that the humidity wasn't high enough for them (even though it was for the zebra finches?? Who knows

) Once they are moved into the garage, I wanted to also place a humidifier near the breeding cabinets to keep the humidity high enough for egg hatching to hopefully enable me to get some owl finch babies out of this pair. This all seems rather counterproductive if the AC/heater is also a dehumidifier, wouldn't you agree?