I am trying to decide which day to book this dinner- from which park (MK, Epcot or MGM) are we the closest- the least amount of travelling time- and how do we go about getting there?
Just to amplify on that, you're much better off walking back from Contemporary to MK if you're trying to make it fast. The resort monorail from Contemporary will go to the TTC, Poly, and GF, before hitting the MK.
If the weather is nice you are better off walking. We stayed at CR last year and walked back from MK almost every night (to avoid the wait). It's about 5 - 8 minutes and a great way to burn a few calories before the meal .
If you are not wanting to go to a park, you can take the monorail and explore the Christmas decorations at the other monorail resorts. The Grand Floridian is breathtaking at Christmas!