ODDA Storage box with casters - $80 at IKEA. I'm envisioning a bit of a hack for this piece--remove the casters, and it's an impermanent but unmovable, baby-safe bench. Hinged storage boxes pinch little fingers, but a little creative construction, easy-to-construct box, and drawer slides turn this box into a bench with storage drawer. An DIY upholstered foam pad and velcro strips make for soft seating (and head-cushion for falls). A row of these under the bank of windows would be perfect!