Check with local building codes about which way the new door has to open for egress if the room is used as a bedroom.

If the queen bed will be used infrequently, you might consider a raised inflatable bed for about $200. They are quite comfortable. Another option, of course, is a queen sofa bed. Ikea may have one- looks like you have an Ikea Poang chair already. A queen murphy bed might fit. Many people find futons unbearably hard, so I'd skip over that option.

For decor, start with your upholstered furniture and flooring to pick colors. It often helps to start with a great piece of art. Or you can start with Lego colors as a cheerful and easy choice for the next few years.

Try a corner queen bed in that large area by the stairs. It can serve as a lounging and reading area when there are no guests. Instead of toy clutter, do some built-ins under the angled ceiling at the sides. Drawers, shelves and containers can help control clutter. You won't lose much square footage doing that. Fill the window end of the room with a seating area and let the kids play in the center.

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