It is totally your personality that will define what you do. All of the parks are great. Just make sure to utilize fast pass 30 days ahead (60 if staying at an onsite hotel). Know that they will add hours as time gets closer, too. We are going mid-November so still waiting on what is going to happen. Is Rivers of Light going to be there? Is Animal Kingdom going to be open late? They will even add hours on that day or only days ahead of time. I am very good at utilizing the app, on my phone, and it slipped by me that Magic Kingdom hours were extended one night. I rode by in the monorail, saw it was open, and changed my plans to hit that park late! I prefer staying out later and sleeping in. I feel that works better for adults. But do not be afraid to master the App.
Spend the money and do a Very Merry Christmas Party! Free cookies and no ride wait times!
Hit the thrill rides: Tower of Terror, Rockin' Roller Coaster, Everest, Space Mountain. Make funny faces at the camera, lol. If you go late at night, or utilize Extra Magic Hours, the lines are shorter. Right near close, you can ride them over and over again without much of a wait. Especially Extra Magic Hours, where only people staying on site can get in to the parks. Yes, it is true, if a park is open late, it is the only place to be, and can be crowded at the start of the late hours, but as time winds down, it empty's out. Also remember, many of the families, with kids, go home. Extra Magic Hours means they extended park hours only to hotel guests. Often they keep the parks open later for everyone and that is when they add more time the day of. Either way, these work best, for shorter lines, at the parks that stay open past 9pm.
Then hit the less thrilly thrill rides, Mine Train, Splash Mountain (my favorite), Thunder Mountain (if you are going late November, as it is under refurbishment and is supposed to open the 19th [hopefully sooner]), Dinosour is even a bit scary, Test Track, Soarin' (New movie and an extra theater now for less wait times!).
And don't be afraid of the nostalgic and less scary rides. They are still fun for an adult! Pirates of the Caribbean, Walk the Tree House near it, Haunted Mansion!, Kali River Raipids (you might get wet), Kilimanjaro Safari, It's Tough To Be A Bug is a fun movie ride, Frozen, ect... You really won't know which ones to avoid until you try them all! There are a lot of the rides my Fiance and I do not ride, but you have to try them for yourselves! Some, like the boat ride in the Mexican Pavilion, are so cheesy that they are fun in their own weird way. As long as you go in with a happy heart and an open mind.
Obviously drink and eat around the world at Epcot. If you can, pay the money for a dining plan! I believe it makes the trip so much more fun. Some of the more sought after restaurants are booked (Be Our Guest, Ohana, Chef Mickey's, among many others) but don't let that discourage you. Keep checking for reservations multiple times a day. It is just 2 of you, so there is more of a chance. Check for reservations at Be Our Guest for breakfast or lunch too. Those are quick service meal credits and therefor less money. You have to see the Ballroom and the West Wing!
Spend a day relaxing at Typhoon Lagoon if you want. Then go out at night to a park.
Check out the resorts! They are cool to see. And each gift shop will have their own unique items. Maybe take a boat from Magic Kingdom to Fort Wilderness and The Wilderness Lodge. Ride the Monorail to Polynesian, Contemporary and Grand Floridian. Check out the Beach and Yacht Club. If you like Sea-Food, Cape May is delicious.Check out the shops on the Boardwalk and then walk into Epcot. All three of those resorts are walking distance to Epcot.
Obviously check out Disney Springs if you like to shop.
Don't be afraid to take pictures with characters!
The moderate resorts are cool too. I love the restaurant at Caribbean Beach. Not well known but amazing steaks. The restaurant at Coronado Springs has a guy playing guitar at night and they have tequila samplers.
Just remember, if you go in and just wing it, you will be waiting in lines and not having as much fun. Make sure to plan ahead. It is overwhelming but do not give up. We were all there at one point.