If they'll be free range, I think I'd just go up with their coop, make it more tall than wide. Make enough room so each bird has 2 ft of roost space and a place for their feed to stay dry. Mine pretty much just sleep in their coop at night. Its really large, it used to be an old hog pen and has several large breeding stalls with a walkway in front of them (probably 50x100), and they're hardly in there at all. They share that space with 16 guineas and they all pretty much head in just before dark and stay in until I open the door in the morning.
The only issue, if you choose to cut space in the coop, will be if there comes a time when you have to lock them up (like, say, if you have an issue with a roaming dog or they're wandering into your neighbors yard). If you have to keep them locked in for a while, they might get testy without a lot of room.
My advice would be to to make your coop as big as you can afford to make it. Or maybe start with a pair or trio instead of 5.
Good luck!