Since you will no longer need the sunroom as a playroom with the upstairs conversion, what about if you turned it into a mostly open, walled patio. It would be a great natural extension of living space. Instead of having the lr and den look into another closed off room, it would look onto a patio. I agree with you that it is awkward to have a window look into another room. This would be a good compromise. It is a porch that functions more like a room.
My neighbor is a gay architect--he did this and lined the top inside with rods for curtains. They stay open most of the time, but if you want to sit out there in your pjs, you could close them.
I don't think this would be expensive--just removing windows/back door and leaving the corners.
Think of this space as a great place to have coffee in the a.m. or a place you can read while you watch the kids play in the backyard. You could also use it as a potting shed with a trunk disguised to place to put all your garden tools. It would be a place to protect your tender plants in the winter. It would make it a more functional room.
With cute potted plants (think pots of red and pink geraniums) and landscaping (sweet smelling star jasmine vine climbing the posts) it would make the view from the den window lovely. If you planted some gardenia bushes too, when you opened the door/windows in the spring it would smell lovely in that room.
I'll put some pics of plant possibilities in the next post.
