I’ve been there the last few Christmas weeks. The days leading up to Christmas tend not to be that bad, and Christmas itself also not ridiculous (although still very crowded). It’s December 26th through 1/1 (maybe a little bit past 1/1 given how it falls this year) that is ridiculously crowded. AK will be the least crowded, but other than that I don’t know that there’s much you can do to “minimize” crowds through park selection. Just go to whichever park you want to on a given day. Go in expecting them all to be very very crowded. You’ll still have a good time, it’s a great time of year. Purchasing LL’s are a must, and they will be very expensive. Using mobile ordering is a must. Eating your meals at slightly off times (or else having reservations) is a must. Trying not to use park transportation at exactly park open or close is a must. Finally, knowing which bathrooms are the less popular ones is a must.
The “less popular” bathrooms at MK in my experience are:
1. Gaston’s Tavern area;
2. POTC store bathrooms;
3. Tiana’s (although this was when Splash was closed, so who knows now);
4. Space Mountain area.
Make sure to place your mobile orders hours in advance (you can always modify the times or cancel them).