... I've got to Boogie... and luckily, there's plenty of fun to be had in December. I'm usually there the first week of December, and I've never noticed Pleasure Island closing early. There have, generally, been smaller crowds, because of the lesser crowds everywhere in the kingdom, but it's still hopping! Also, I love heading over to The Boardwalk for a night at Jellyrolls (featuring duleing pianos and lots of folks singing along). You can also head over to Port Orleans Riverside to see the entertainer in the lounge there (although call ahead to make sure he's on that night and what the hours are). Earlier in the evening, you can head over to Fort Wilderness for a hayride, or movies, or the campire (and making smores!). I've been to Pleasure Island until as late as, oh, maybe 2 in the morning, and been able to catch the last bus back to my resort. But even if you miss it, you can easily catch a cab and it won't prove to be very expensive.
Have a great time!
Richard