Welcome aboard, and kudos on picking a great time for your trip. I think you will have a wonderful experience.
Just some tips from my perspective:
1. Make sure to take time to explore the resorts. They are beautiful and really add a new level to the adult nature of WDW. If nowhere else, take an evening after the MK to explore the Poly and the GF, walking along the beach. Also, try and sneak over to the Boardwalk area one night (BW, Swan & Dolphin, and Yacht & Beach club). These are both connected to MGM & Epcot, so that can be convenient.
2. Don't feel the need to see everything. You have a nice chunk of time at the resort, so you will see a lot. But, there will be things you miss. Don't sweat it; you can see it next time you go. The point of Disney is taking in the atmosphere and really enjoying that (either for relaxation, trying "figure out" the details, etc.). The attractions are a huge part of that, but the individual attractions are secondary (albeit entirely tie in) to the overall atmosphere IMHO.
3. Depending on the type of person you are, you may enjoy doing some quick research on-line about hte history of the parks. All of the parks, especially MK and Epcot, have very deliberate design elements. If you like history, engineering, civil planning, or anything like that, it adds a WHOLE new part to the parks. You really come to appreciate the thought that goes in if you see where it was, is, and may go to someday.
4. Take advantage of the holiday offerings. MVMCP, although an upcharge, is a lot of fun. Being a Mickey fan, I would say it is a must see for you. The Candlelight Processional is also wonderful. Although it is the Christmas story, people of all denominations can enjoy it because it has a wonderful narrator and huge chorus. It makes for a great story and show (regardless of your personal beliefs). Same goes for the storytellers around Epcot. While I am probably biased, I truly believe Epcot offers some of the finest holiday entertainment anywhere. Take at least two nights here to see everything (and see it again).
5. Read through the threads here. You will find many, many little treasures and tips. Even finding a couple of these on your first trip will help show you the magic that each of us (obviously) holds so dear.
Have a wonderful trip, and please come back and let us know how it went!