You're missing the third room dimension.
You COULD use that as intake but it would require the vent to be split and the ducting to make it acutally work would be pretty much a pain in the ass. Try an intake from the living space in your home instead. If you are worried about damaging doors, get a used closet door and cut a hole in it, then put the old one back up if the in-laws come to visit lol!