Start with the play area upstairs when young, but I think I'd prefer upstairs to be the bed and have the downstairs for play, and eventually a desk and workspace when they get to school age.
This is what college dorms should be like. So cool.
Bed in a Drawer
20 ideas on displaying books in children's bedrooms. I love this chair and bookshelves for my own room!
Frederic Lucano interior portefolio