There's a Grinchmas acting production at Islands of Adventure throughout the day. Haven't seen it so I don't know what it entails. They also have a special light-production show outside of Hogwarts Castle in the evening. Although I'm not really clear if that Christmas light-show replaces the regular light-show, or is in addition to it. And if the DarkArts show is something in addition to THAT, or if it's just another name for the same lightshow.
Depending on how often you go and when, you may want to upgrade your AP for EP after 4. We did this (and we live in Iowa), but it was cheaper to upgrade than do one day of EP. Yes it doesn’t start until 4pm but we were able to a lot of things without the EP first then did a lot more after 4. This was 4th of July week too