Whatever you do, don't do tile! I am a fairly active older person in pretty good shape (yoga, walking, etc) and if I spend more than an hour in the kitchen standing on tile my body starts to hurt! This started happening last year and I realize it's because of the tile (on slab) I am standing on. If I could do it over again, I would either do engineered wood like the rest of the house or Marmoleum, which I have a "thing" for. The hardwood I have in the other room has grooves but they do serve a purpose which is if you get grains of sand for example they go into the groove and prevent abrasion of the planks themselves. It's like a little "collection area" for dirt. The dirt vacuums out quite easily. The engineered hardwood I have is Mirage and it has held up well over the past 7 years. There are nicks and scratches from use, but that is the beauty of hardwood. If you buy good quality hardwood floors, they have a couple of sandings in them and I believe they can have many many screenings.

I was on what felt like my death bed last week (ok a bit hyperbolic!) so caught up just now and the floor looks great! I like it a lot and think you made the right call. I like the idea of a painted island, creamy white would be nice but don't rule out color. As for the appliances not matching if you do a white island, that problem goes away with color for the island. You may need/want to replace your appliances sooner than later but I would not let the island bully me into that even if you go with a white. It might not be ideal but you can change the appliances at a later point.

Are you planning to be there long enough to ever refinish the floors? If so, the thicker veneer might be better. Otherwise, I'd choose the one you like most. The bellawood appears to have a lot more variation in the planks, and doesn't seem clear regarding the finish. The grand pacific is a little more uniform, with a good UV finish.

The question becomes, do you WANT to change out your dark gray floors? How old are they? Are they in good shape? What APPEARANCE of flooring are you hoping for in the addition? Example: if the addition is getting a wood-look product, then it is a fashion faux pas to pick a DIFFERENT looking wood-look product. This is where a site-finished hardwood saves money in the long run. You can always sand/refinish a solid hardwood for about $5/sf. If you have to remove (labour + disposal = $1.50/sf) all the gray flooring and replace (labour = $2.50 - $3.50/sf) with new flooring ($7+ for decent quality wood or LVP) then you are getting into TWICE the cost of a sand/refinish. OK...I digress. If your BUDGET allows for it (read $10/sf total costs) then the IDEAL solution is to have the SAME FLOORING throughout both spaces. To DO THIS, you MUST tell the builder to MATCH the subfloor heights. When conversions happen it is often with an UNEVEN subfloor height. It CAN be matched but you MUST declare this to the builder BEFORE they start the job. And be prepared to pay a mark-up. If they need to go to a more expensive plywood because of THICKNESS, you will need to pay the extra cost for such a change. And right now the costs of wood are EXTREMELY HIGH. As in plywood has QUADRUPLED in price over last year. Just a little FYI for your planning stage.