Greetings, I'm getting ready to expand my gourmet mushroom farm, and I need some help figuring what to use. I'm thinking a mini split or heat pump, since I can use them for heating or cooling....

I'll be setting up a "green house" inside of a warehouse <-not insulated. and I'm in Georgia so its in the upper 90s at the hottest and winters aren't too cold. I'll be humidifying the green house with a compressor driven fogger, so there is some evaporative cooling effect, the dryer the air the more this effect cools it.
I can insulate the green house if need be.
-I only need to cool the green house.
-I'm running fresh outside air through the greenhouse at 500-800 cfm at all times.
-I'll also recirculating air from the greenhouse.
- I'll be running at 50-60 degrees in the winter and 69-75 in the summer.
-Green house is between 6200 and 6600 cubic feet.

I was thinking of a large "mixing box" that I could put two mini split units right inside of, and run outside air into that, then run the mixed air into the grow room. possibly use a heat exchanger.

Should I go with a heat pump and just pipe the cool air right in? What size?
Can I get away with a mini split?
how do I make a mixing box.
Thank you!