You certainly could, but hardwood flooring is designed to be nailed to a solid substrate and the typical T&G edges don't present a good gluing surface--they're only approximately in contact. Flooring needs to be able to expand and contract with the seasons, so the boards are not glued to each other. Unless you have a cheap source of flooring I'd just make the top from regular walnut boards that haven't been milled into flooring. Butt the edges together or use a few biscuits for alignment and you'll quickly have a beautiful top. I have made such tops from leftover flooring, but have ripped off the tongues and grooves to recreate planks with square edges that can be properly glued. You don't want cracks opening and closing in your desktop, so it needs to be attached to the frame so that the whole top can move, not the individual boards. Desktops take a lot of abuse, so I'd consider a more rugged finish, either an oil-based polyurethane or seal coat of amber shellac followed by several coats of water-base polyurethane. Let either dry thoroughly and then rub it out with 4-0 steel wool followed by pumice/rottenstone then wax to achieve a silky surface with the desired level of shine. A little yellow in the finish helps pop the color of the walnut.

I am answering not from a place of how any of these stains look because my taste is terrible. With that said, I would pick a medium stain over a dark stain because dark floors show everything, and I have neither the time or the energy to try to make them look nice.

It looks like the floors have been stained/finished to match the cabinets. If you must refinish them (and I would ONLY do this if they ABSOLUTELY need it) I would work with a water based polyurethane. Just as dcarendt has done, going NATURAL with a water based finish will offer a degree of separation which would be JUST ENOUGH to offer some visual interest. Personally I think the COUNTER TOPS need changing more than the floors. My first choice would be a CRISP white (no gray) or a soap stone/slate counter top would be EXTREMELY handsome. You need some CONTRAST in the kitchen. Right now you have mid-tone sitting on mid-tone sitting on mid-tone. You have the lightest version of "brown blahs" I have yet encountered. Changing the counter tops would be faster and probably cheaper than changing the finish of the wood.

Decluttering before redecorating/remodeling is a good motto. Your kitchen is warm looking but all the stuff on the countertops is unappealing. I'm confused as to why decluttering is more of a challenge than renovating the kitchen, a massive expense consuming months of family time! If necessary, hire an organizer to do declutter for you--money well spent. This will give you a fresh eye to see how attractive your kitchen actually is and how to make the most of it before you spend a fortune in money and time to gut it. When you've gotten rid of duplicates of things, then consider putting in Rev-a-Shelves in some of the lower cabinets to increase functional space. Get carousels for upper cabinets. The countertops are beautiful and go well with the cabinets. Add some under cabinet lights if you don't already have them. Consider adding a backsplash of rippled subway tile in a warm cream color that harmonizes with the countertops. This will lighten the kitchen hugely along with undercabinet lighting like this kitchen with dark countertops creamy backsplash and wall color: Since you have adjoining spaces opening up near the kitchen, consider painting all the walls throughout a warm white that you pull from the background of your countertops. This will give you a feeling of flow and lightness--no need to repaint the cabinets. You have some beautiful wood floors in your house. Refinish them in a stain that goes with your cabinets so everything flows from room to room. Yes, the kitchen floor tile isn't an ideal choice with your warm cabinets. Once you declutter, get an attractive indoor-outdoor rug for now with golden tones and colors. As for gray floors, why? You have warm, golden floors elsewhere. If you're changing out the kitchen floors down the road, then find a floor tile that harmonizes with the wood floors you will have elsewhere.