First, a disclaimer. I am very tired as I type this and it has become too long for me to adaquately proofread. Therefore, please disregard all typos and other English mistakes made in the following. Thank you.
Since I won't be returning again soon, I like to plan. So I'll help you figure this out. It's like a puzzle. OK, here goes.
MK has early hours every day in Dec. for the week you are there. It also is the more popular park, so I would wait and head there in Jan. Come Jan. 2, crowds should diminish greatly. I would head there Jan. 2, 3, &/or 4.
EPCOT and Animal Kingdom, though crowded, can probably deal a lot better with said crowds. They are the larger two parks and can probably hold more people. In EPCOT, there are lots more exhibits and (what I call) personal experiences to be had. You can tour World Showcase at your leisure, crowds or not. There are only 2 rides in WS and most shows hold a lot of people and run every 20-30 minutes or so. In Animal Kingdom, get there like an hour prior to park opening. There is an opening celebration and it is worth it to be early - you can get great pictures with the Tree of Life in the background. Once the park opens, head straight for Africa and Kilimanjaro Safaris. This will become the most crowded attraction and the animals will be more active during the morning. Get there first thing and get right in line! With the use of FP, the rest shouldn't be that bad, since there are more shows and animal experiences here than rides (per say).
In any event, I would head to EPCOT Dec. 28 and/or 30 (non-EMH hours) and Animal Kingdom on Dec. 27 or 29. On Dec. 30 & 31, enjoy the holiday decorations. Or consider heading to Downtown Disney, a water park, or having meals at one of Disney's wonderful resorts. One of our favorite things to do on our "break days" is to eat at different resorts and ride around on the monorail. While the monorail may be crowded, it's still loads of fun and FREE after all!
As far as MGM, my best bet would be to head there in Jan. as well. This is a very small park and gets VERY crowded. Was there during Super Soap Weekend (actually NOT to see Soap Stars, hoping lines for attractions would be shorter) and it took forever to move from one attraction to another. There were people everywhere! Also, there are fewer attractions here, so each will be more crowded. I'd wait until Jan. (maybe the 1st?). Many people may fly home that day to return to school/work/etc. on Monday!
I would DEFINATELY arrive as soon as the parks open. We always do this on all our trips and tend to have fewer crowds for awhile. Spent a Friday recently in MK and here's how my day went: Arrived at park opening (which was an EMH morning), rode Peter Pan twice, Winnie the Pooh twice, Snow White, Mickey's PhilharMagic twice, = all during EMH (well done at about 9:10 AM), Splash Mountain 2 or 3 times, Big Thunder, & Jungle Cruise all by 10:00. Left and went to another park until about 1:00. I came back and saw wait times of 60+ minutes on most of the rides I'd been on earlier that morning. While I had been there, I grabbed FP's to return later. Used the 3 FP's, had dinner, & left b/c it had become too crowded.
I would recommend getting there right when the parks open (actually about 30-45 minutes before). Most open at 8:00 that week. Stay until like 3 - 4:00, leave and have dinner in a resort or have dinner somewhere in the park. Leave your nights completely open. If you want to return and see the nightime entertainment, GREAT! If not, relax back at your hotel and return for opening the next day. I wouldn't arrive mid-day and see if the parks are filled to capacity by then.
I would also definately plan out your meals. There are websites with menus of all the restaurants in WDW and call Disney to make ADRs (Advanced Dining Reservations). Do this ASAP, as popular places fill-up quickly. ADRs are a free service and most restaurants won't charge you if you do not show up. (It's mostly just the dinner shows and more upscale restaurants, but check with Disney for the exact list).
I'd definately plan out your days before you leave. I always try to make a list of the attractions that are "Must Sees" for my group and "If there's time, we should see" attractions. This way, you've got your bases covered. Realize that you cannot see everything. Also, get FP's as often as possible. If you receive one for an attraction and it says you can get another one in an hour, try to do it! I can imagine FPs will go really fast!
Speaking of which, if Soarin' at EPCOT is a priority for you, head there AS SOON AS THE PARK OPENS!!! I cannot stress this enough. I was there in Nov. It was crowded, but nothing like Christmas. Went to EPCOT on Thurs, FP's were gone for the day a little after 11:00 in the morning. Went on Fri., arrived at 9:45, FP's had been gone for the day for quote "a little while". The park had only been open for 45 minutes! Went to EMH on Thursday night in hopes of riding it. Entered at 8:45 (thought crowds would be lower during Illuminations! at 9:00), still waited over an hour! People have been waiting 2 or even 3 hours to see this! It is a really great attraction - one I highly recommend. So head there first thing on your EPCOT day! Another reason to get to the parks early.
OK, to recap.
1. Get to the parks 30-45 minutes before they open. A lot of people will not be able to get their kids and family members to a park that opens at 8:00.
2. Avoid parks that have EMH hours - it will just be too crowded!
3. Use FP whenever possible - try to always have one!
4. Head to EPCOT & AK during more crowded times, as they will hold more people. Head to MK & MGM during less crowded times.
5. Make dining reservations in advance - you can always change/cancel!
And most of all, have fun! Hope I helped.
aw:
aw:
I know that the week after Christmas is super busy. I know that the parks may fill up. However...we are bringing a first time guest with us for the first week only. We want to show him the most we can. My question is...What parks do you think would be our best choice for the day... The park that has early opening and get there when it opens or choose another park for the day. We are not getting park hoppers this time. We are planning on checking out the decorated hotels and soaking up all the holiday fun. 
