Awesome Loft Beds--Since you won't have a window on the one end of your upstairs, this could be a fun idea for the kids area. Not necessarily a bed, but a 'loft' on top of a 'hide-out' area---or something. The bookshelf stairs are a neat idea too.
Attic Bedroom Closet Design, Pictures, Remodel, Decor and Ideas - page 9 - sublime-decor. I have the perfect wall (with attic behind it) to do this. I've often thought of making an easily accessible closet there.