A Budget-Friendly Craft Room: could put two book cases on either side of the window or wall. then use a folding table coming out like this from the window. Table that folds up? Adjustable height as kids grow?
Laundry Dresser folding area and hanging shelf - such a great idea! Last pinner suggested "Build it in two sections and add casters to the bottom so you can roll it around and it will be easier to move.