It will work fine. Lots of folks have done this. You can probably find examples in the coops section -- click "coops" in the brown bar at the top of the page. Use hardware cloth (wire mesh) to cover windows, to protect from predators. It's best to find a way to ventilate it at the highest point of the playhouse. This lets humidity and ammonia escape. You'lll probably have to cut a hole and cover with hardware cloth -- a bigger hole than you would think. Even in winter there needs to be good air exchange at the vent, though it can be closed up tight everywhere else. You may not need a solid cover for the window, depending where you live. Chickens tolerate cold a lot better than heat. The lower part of that door should make a good chicken door.
Here is an excellent article on ventilation