Hi from a neighbour, Tigger2on! Last year was my 11th visit to WDW, but the very first one we'd attempted during the Christmas/New Year's season. We arrived on the 28th and left on the 4th of January. I have to admit I was really worried about the crowds before we left.
I decided that the worst days to manage would probably be NYE and NY day, so I worried about them first. We decided (with younger children) not to spend NYE evening in a park, so Animal Kingdom was a perfect choice for that day - not very crowded at all, and we were able to ride Kali River Rapids 5 times in a row during the last half hour the park was open. That evening we'd planned to see the Luau - BAD CHOICE! - since it got rained out and we had to scramble to find something, finally ending up at Maya Grill at 9:30 with my son falling asleep at the table. Moral of the Story: Do not choose outdoor entertainment for your New Year's Eve celebration!
We decided on Epcot for New Year's day, and that was another good choice. Epcot it just so big it can absorb a large crowd.
On the downside, though, MK was very crowded on both of the days we visited. They were both EE days, and I'm not sure to what extent that played a role. The crowds were huge, and became overwhelming as we walked into Frontierland and were met by a surging mass of bodies trying to exit the area (both Splash and Big Thunder had broken down at the same time). That was the only point at which I hung on to the children for dear life and felt like a human sardine.
We made a PS for every day, used fastpass a lot, and tried to get to the parks as early as possible. If you're staying on-site, it's worthwhile to make two reservations - one up to the 31st, and the other starting on January 1st, when the value season rates go into effect. CRO will link your two reservations so that it's very unlikely (though theoretically possible) you would have to move within the resort.
On the whole, it was a great experience, and as a matter of fact, we'll be heading down the I-75 on December 27th this year, too.
Have fun!