Hopefully Art the Greeter is still there. Make sure you say hi to him and get a picture with him. He'll even sign autograph books!
The only bad thing about BC during December is that it most likely would be too cold to comfortably swim, which is too bad for a resort known for its pool. People will disagree with me, but I prefer not to swim when the high is maybe in the low 70's and lows are in the 40's and 50's. Yes, Orlando cools off in the winter. We've been there many times in December and January, and while low 70's is awesome for park hopping (no humidity either), I wouldn't go near a pool in the middle of summer if the temps were in the 60's or 70's, even a heated pool. You can have days near 80 or so in temps, but those are actually pretty rare in central Florida that time of year. More realistically it would he highs in the upper 60's and maybe lower 70's on warmer days. And I'm here to tell you, no matter how much Disney may claim the water temps are uniform year-round, that just is not the case. Fortunately, if we go in winter, we don't expect to be able to swim, so we're not disappointed. Keep in mind, most times when we go in December/January, the usual highs are in the upper 50's to low 60's. Again, that's great for park hopping, but not so much for swimming. I've been in December with a high of about 45 degrees and a constant 25 MPH wind. Be prepared. But then it was about 15 degrees that same day where I live.
If you do go to the pool, though, I agree with the PP about the mini-slide across the walkway.
Walking over to the Boardwalk area is fun for a quick bite to eat.
Keep in mind that you do not have to boat over to MGM or EPCOT. Walking to each one is probably actually faster, and the scenery is lovely. But if it's a cold day, the boats might warm you up a little bit.
If you bought the park-hopping option on your tickets, you can walk into the WS section of EPCOT for dinner, then come right back to the resort, if you like. That's handy.