Hi Brooke,
Mickey's Very Merry Christmas Party is an awesome way to celebrate the season. You can find a general list of events on the official Walt Disney World website at the link I've provided here. But let me try to help you with some other information.
The party runs from 7 p.m. to midnight, but guests with party tickets are admitted as early as 4 p.m. I'd suggest getting inside no later than about 5:45 p.m. so that you can be in place to see A Frozen Holiday Wish at 6:15 and the lighting of Cinderella Castle.
Most of the rides and attractions remain open throughout the party, including the new Seven Dwarfs Mine Train, all three Mountains (Space, Splash and Big Thunder), Pirates of the Caribbean, Princess Fairytale Hall and more. The Jungle Cruise has transformed to the Jingle Cruise for the occasion.
A couple of tips: Dining is limited to select quick service locations during the party. I like to eat ahead of time so that we can spend all of our time enjoying the party events. (And, you need room for the free cookies and cocoa.)
Also, it's good to have a general itinerary in mind so that you don't miss something big. Make sure you see the parade, Holiday Wishes and the special edition of Celebrate the Magic (the Castle projection show). And you don't want to miss a walk down Main Street in the snow.
Many of the unofficial sites have scanned and posted the official guide maps. You can find them by searching "Mickey's Very Merry Christmas Party Guide." AllEars.net is one of my favorite unofficial sites. It has the map and other information you may find helpful.
Thanks for visiting the Disney Parks Moms Panel with your question. Please let us know if we can do anything else to help. Enjoy the party and your holiday at Walt Disney World!
Wilma