There is no one single resort that's best for all kids, especially when it comes to really little kids like a 2 year old that, in all likelihood, never really remember a thing about the hotel or the trip. Case in point, when my youngest was 2 we had a trip where we stayed at Bay Lake Tower. By the standards of a lot of forum members, Contemporary and BLT are great on location, meh on theming, even though it's a very nice hotel. She absolutely loved it, but that was in part because of the excitement of the trip in general, the fun things we did on the trip versus in the room or even in the resort (but of course anyone can visit any resort). The one big thrill? The pool (it was an August trip, not a planned December trip like the OP). For months afterward, as she went from 2 to 3 and her vocabulary got better, she would ask "Daddy? Maybe this weekend...we can go to Disney? And we can go to the hotel? And we can swim in the pool? And I can go down the slide and you can catch me?"
It. Was. Adorable.
She is now 6. She does not remember hardly any of it. And a lot of the memories she has are "implants," meaning she recalls more based on our telling of OUR stories rather than her own. She does not remember asking to go down the slide (and we're talking the baby slide, not the "big kid" slide), she remembers me remembering. She does not remember meeting certain characters, but she loves the photos and hearing our stories and her big sister's stories about the trip.
Similarly, our prior trip, my youngest was an infant, her big sister was almost 4. Big sister might have been never funnier than that trip, some of the things she'd say, in front of other people, were so cute, some guests only-half-jokingly asked if we were "Disney plants," coached to be so adorbs in order to give other people warm fuzzy memories of Disney. And SHE doesn't remember any of those moments, beyond our retlling of those moments.
None of this is to say "don't factor your kids' interests into your decisions" or "why bother going if they'll barely remember it, or not remember it at all?"
But stay where YOU want to stay. Part of what will make good memories is how good a time YOU had, too. They're going to pick up on your vibes. Factor where you plan to stay most of your time, what sort of amenities would be convenient, a must, or completely unimportant. Factor transportation if you won't have your own car, especially if you think you might need to head back to the resort in the early afternoon for nap time. Factor your comfort (my wife and I are not petite people and sleeping in the double beds in Value rooms is a miserable experience for us. If they have no prior stays to compare this one to, it's not like if you stay at AoA they'll go, "meh, not as good as the time we stayed at the Wilderness Lodge. Try harder next time."
If indeed money is no object, I'd suggest a monorail resort so a: you're closest to the Magic Kingdom; b: the monorail is in itself a "ride" for kids, and many adults and you'll also be able to use the monorail to get to Epcot; c: it will afford many more options for meals that are easy to get to; d: the rooms are bigger, beds are more comfortable; e: if you're going in December, this makes it easier to "resort hop" so you can see how the resorts gussy up for thr holidays.
Grand Floridian and Poly probably have "cooler" water playground options than Contemporary/BLT, but it will be December so no guarantees the weather will be suitable for swimming. Staying at the Contemporary not only gives you monorail access to Poly & GF and MK and Epcot, it also gives you boat access to Fort Wilderness & Wilderness Lodge.