I think window treatments fall into two categories: The Practical: you have too much sun and need some shade because of the glare. You need privacy. The Decorative: many people use window treatments sort of like eyebrow pencil, or putting a scarf on an outfit--it finishes the look. Also, it can be used to add color and/or texture. It sounds like you are more in the "decorative" category. So, if you don't feel it would add to your kitchen in any way, I'd skip it. Plenty of kitchens don't have window treatments and they are beautiful without them.

Thanks for clarifying the use of the space. It originally sounded like a room for the kids mostly. I think it is nice that your DH likes to be involved. Plaids and checks are hardly just country, but if that is his thought and he is immovable on that, so be it. LOL I was confused by your comment about the swirly wall areas not being able to be painted. They are painted the ceiling color, aren't they? No special maintenance to paint them another color, and I really think it would make the room feel more spacious if they were the wall color. I like the changes you have made - the room feels so much brighter.

First question is do you want window treatments for decoration? light control? and/or privacy? First blush, I would use coordinating but not matching fabrics on the slider and the bay window and I wouldn't treat the door at all. If I had to treat the door, I'd look at the double shirred or the encased blinds. On the slider, if I needed complete privacy, I would put a large valance, off centered, across the top and stack full length drape panel to one side only so that they will stack back completely onto the wall during the daytime and shut all the way at night. On the bay window, you have the option of treating the front of the window only, or treating the windows themselves in an angled fashion. I did the latter with my bay window.

Since you have the cranks on the windows and need access to them, I wouldn't put anything there. Valances can be old fashioned and your windows are more contemporary. If I didn't need privacy, I would forego window treatments. The views are nice, but if you don't want to see the deck and its furnishings, try an inside mounted semi-sheer cafe curtain on the tall window. That still allows a view of the trees, but will block the deck and railings from sight. Add color to the kitchen with some colorful hand towels, pot holders, crocks/cookie jars/canisters, a kettle or small appliance. If you limit the items to a few decorative accessories, you can change them out when you feel the mood or the seasons change. Pops of orange A bit of lemon Turquoise