Having the garage makes this pretty easy to keep quiet! :thumbsup:

I'd grab an 8" or 10" centrifugal to mount out there. The bigger the fan, the slower it needs to turn.
In the tent, you could "Y" off after reducing to 6". Run the light "sealed" straight thru, pulling room air, with a baffle on that leg. The other leg, you route to the carbon filter, to exhaust the stale tent air.

You could baffle both legs for more control, but I would run the blower with a speed controller and the one baffle on the light. A duct muffler on the line to the blower would further reduce the sound, as would insulated ducting out there. It should be whisper-quiet.
(unless you have leaks, then it might whistle)

With the main exhaust out there, the loudest thing in the tent would be your oscillating fan. :thumbsup: