I think the whole second floor balcony sounds great! Make sure you have enough support, structurally, for the balcony to hold up at least 3 inches of sand. This stuff gets HEAVY! Also, try to figure out where the sun is strongest in the summer and "wall" that off-a good place to put their coop. Also, once its gets screened-in, cover it over with a cute canopy overhang to keep things dry. Don't forget to add a small seat for yourself to sit there and enjoy the company of your girls!