First, I want to say how exciting that sounds to stay at one of my favorite resorts during the holidays! I was so stunned when I walked into their lobby for the 1st time & took in all of the decorations & music. If it was ever in my budget, this would be my top choice for a holiday trip on property.
If you have never done it before, book the Candlelight Processional Package so you get a nice lunch or dinner, reserved seating & a Christmas Illuminations FP.
I would also recommend sleeping in & staying out late b/c all of the lights & decorations are pretty at night to make the most out of it & later hours. You can look at the times guide for WS & plan to see some of the holiday stories in the countries you're interested in. Some of them are pretty good IMO (Tip: get a warm Glühwein from the booth in Germany to take w/you for the stories..it's my favorite holiday drink in Epcot & it sets the mood).
Things that I do regardless of the holiday season w/no kids:
~Whatever I want, Whenever I want to do it!
~DTD at night is always fun. I like to hang out at Raglan Road when they have the band outside on the patio (they have outdoor heaters if it's cool outside).
~Take your time in the parks to explore & take it all in.
~Stop to see the World Showcase Players in the afternoon at the UK Pavillion.
~Go & enjoy a Dole Whip w/rum at Tamu Tamu Refreshments in AK!
~Go to karaoke in the evening at the Swan's Kimonos Lounge & have some really good sushi if you like sushi.
~Try a Deluxe restaurant on or off property one night.
~Spend some time at the Tambu Lounge at the Poly & get a specialty drink. I like the Lapu Lapu served in a Pineapple or the Backscratcher which packs a pretty good punch. If you get it to go, stroll around the grounds or hang out at the beach on a swing for a while. They also have some good appetizers on the menu there if you get hungry.