For me, personally, the noise level isn't that bad. It's a big, open room, so all the conversations do seem to resonate in the air, but I've never noticed it so badly that I was needing to scream to my DH. Definitely wouldn't be able to whisper to each other, but you could have a normal conversation level. But you should definitely request the wine room if you choose to go there, because noise will not be an issue at all. And no matter where you're seated (wine room included), you are able to go out onto the observation deck when the fireworks start and watch them from there. They will hold your next course for you so it's brought out right when you are getting back to your table - they time everything perfectly there.
And don't worry about the planning for a Dec trip now - I do the same thing! DH used to think it was 'weird' but then he saw how much fun I had planning everything and now he does it to. He'll come home saying, 'I think we should eat HERE on the next trip.'