Hi Melissa!
I experienced
Mickey's Very Merry Christmas Party for the first time myself last year! It was so much fun.
As you enter Magic Kingdom, you'll be enchanted by magical "snow" falling all along Main Street U.S.A.
Also featured during the party are a special parade which takes place during the party only including Santa Claus himself, a special presentation of Holiday Wishes, a different fireworks display than the usual Wishes shown on regular nights as well as special live shows and meet and greets featuring Disney Characters. See all the details on the link above.
The complimentary cookies and hot cocoa are a fun thing to pick up at some point during your evening at one of the several locations around the park serving them up, but are certainly not the main draw of the evening!
If you haven't experienced it before, it's most definitely worth considering a visit too! It works especially great to do this on an evening that you're planning to do some shopping or resort relaxing during the day. Gives you something to look forward to for the evening!
Another 'festive' activity to consider as a complement to your Mickey's Very Merry Christmas Party evening, would be to make a reservation to enjoy dinner turkey dinner with the trimmings at
Liberty Tree Tavern. You'll be able to enter Magic Kingdom a little earlier than the party start time with your dinner reservations.
Thanks so much for visiting the Moms Panel. I hope you'll visit me again soon with more great questions.
Wishing you a simply Magical time on your holiday visit to Walt Disney World Melissa!
Kirsten