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.
Minimalist White Themed Kids Bedroom Design Ideas with Solid Wood Green Bunk Bed Furniture that have Soft White Mattress complete with the Pillows and Corner Space High Green Wood Cabinet that have Three Doors
The Ultimate Custom Dollhouse Loft, Bunk or Triple Bunk Bed, Optional Trundle, Slide, Step Block Staircase w/ Built-in Storage or Ladder