Hi there, Jennifer!
You will certainly be able to enjoy the 3:00 PM Celebrate a Dream Come True Parade that occurs daily throughout Magic Kingdom.
Mickey's Very Merry Christmas Party is a separate, "hard ticket" event that will require you to purchase a separate entry. The ticket gets a partygoer Guest a wristband, which identifies him/her as having purchased a ticket in advance.
At 7:00 PM, the official start time of the Party, Guests are asked to show their wristbands to Cast Members stationed throughout the Park. If a Guest does not have a wristband, s/he will be asked to head to the Park exit.
But you'll have loads of chances to see the Wishes! fireworks spectacular, Illuminations: Reflections of Earth at Epcot, and Fantasmic! at Disney's Hollywood Studios.
Have a wonderful time!
See you later, celebrator,
-Deborah B.