Hi Ami,
I love
Mickey's Very Merry Christmas Party! It's such a fun way to celebrate the holiday season.
On party nights, Magic Kingdom closes at 7:00 p.m. to regular guests. Then the fun begins. There is a special holiday parade and fireworks, dance parties with favorite characters, cookies and hot cocoa, and and a ton of other special activities. No holiday party would be complete without Santa, and it even "snows" on Main Street USA. Plus, many attractions are open during the party for guests to enjoy!
There is a special map for the event that is available as you walk into the park. If you check at Town Hall, they might also let you take a peek at one ahead of time. I've honestly never tried, but I think they might let you. If you do an internet search for "Mickeys Very Merry Christmas Party map," you'll be able to find one of the guides from last year's party.
Hope this helps. Have a magical vacation!