Which view do you have booked, Theme Park View or Standard/Bay Lake View? This will impact my advice.
I am not sure where the King beds are on that floor... I assume there are not very many of them? I need to research that more. How critical is getting the King bed? If this were me I don't think I'd want to use my request on this because there are other, more important requests, but that's just me.
If noise is a concern, my opinion would be that you generally don't want to be on the Chef Mickey's side, which is the south end of the building. One time we had the second to last TPV room on the Chef Mickey's side and it was somewhat noisy. They play a song / have you wave your napkins every once in awhile. We could hear it in the room with the door closed along with general restaurant noise... plates clinking, kids shouting, etc. It wasn't horrible, but it wasn't great either. DD was 9 months on that trip so I remember it well. She was fine, but my kids will sleep through anything.
Our room last fall was a TPV room on the north end closer to the MK. I much preferred this room and being away from Chef Mickey's, and of course the view to MK was closer. Although you trade off one noise for another. You could hear the dull roar of the bus traffic to/from the MK bus stop. Again, not horrible and not enough to bother us, but it wasn't dead quiet either.
I don't think the 12th floor is "loud", but it is an open atrium hotel so of course noise tends to drift up. It's a fun "I'm in the heart of Disney" kind of noise.
If it makes you feel any better, all Disney resorts have noise in my experience. CR was no different than the others. CR is also one of my favorites!