Thanks for posting pics.
If you haven't bought your plastic yet, here is a site to browse:
http://www.growerssolution.com/page/GS/CTGY/gc
They have a free shipping deal going on right now.
You'll need to make sure that water does not pool in the area above your side purlins. You can weave rope through the space if it does. "Batten cord" is the term. You may also want batten cord going over the entire structure to hold the plastic down in the wind.
You didn't mention the sizes on your windows, but I am going to guess that they will be not nearly big enough. Without roll-up sides, I would want the entire ends of the structure to open, like this:
That's an "Eliot Coleman Scissor door." It's just two pipes bolted together as a hinge.