I suggest simple and modular / multipurpose. Simple to minimize distractions and modular so you can change it up for novelty.
A gate leg table folds up almost flat against a wall but can be pulled out for ample workspace. Cardboard study carrells can give them separate table areas or be folded up for a shared project or big work space.
http://www.ikea.com/us/en/catalog/products/70290223/With bigger built-in storage - I LOVE this one!
http://www.ikea.com/us/en/catalog/products/S09123087/I'd also suggest enclosed storage. My ADHDer does best when he can only see the materials he is working on.
