Built-in bunk beds is a great idea to preserve space. The built-in book shelves also help to create more storage for toys, books and etc. The first step of the ladder has been eliminated in order to add under bed storage/trundle.
DIY Board and Batten Tutorial (in our laundry room
Bed couch with draws, shared room, space saver. this could go in bedroom area. like the shelves idea, too. can add a light wooden dining table and a few comfy folding chairs to make cool dining area in bedrm space, if bed moves to living room area.