I would be wary of multiple fans and air manifolds, you don't want the fans fighting each other for air. If you were going to use multiple fans I'd think the only safe way to handle that would be forced exhaust with passive intakes.
If you've ever hit a hookah-style bong with a friend who pulls too hard you know what I'm saying here. The friend can literally suck the hit right outta you by pulling too hard.
You didn't specify height of the tents, but running some math it looks like you have about ~1000 cuft of airspace to exchange. As @KingGhidora said, I'd link the intake/exhaust ports together in a chain and consider this a single room. If you're doing proper air exchange rates this should be fine with a single fan system. You could even hook 2 on the left, 2 on the right, join them in the center and exhaust from there. That'd give you 2 passive intakes and a single exhaust fan.
If you really wanted to use the extra fans I'd run them inline, just keep in mind you never want to have your fans fighting each other for air.
My grow room is just over 900 sqft and I use a 6" port w/ a single exhaust fan w/ passive intake to control everything. Heat too high, kick on the fan. Humidity too high, kick on the fan. CO2 too low, kick on the fan. It took me a bit of calculating to get it all right but it's been working great. You can get there, just think it though.