Hi Shini!
Welcome to planDisney.
Thank you for asking this question!
Mickey's Very Merry Christmas Party is scheduled for the evening of 12th December. All guests can visit Magic Kingdom on special party days, but if you don't have a ticket for the special event you will be required to leave by 6.00pm. Party guests can enter Magic Kingdom any time after 4.00pm, even if they don't have a regular admission ticket for the park, and will be identified by a special party wristband. The party officially begins at 7.00pm.
The park is reported to be quieter during the day, as some guests would rather save their ticket for a full day when they can stay until closing, and enjoy the fireworks. If you don't mind having a shorter day you might enjoy reduced wait times around the park, and you can still make your Lightning Lane purchases if you wish to do so (but you might not need them).
All guests are permitted to make dining reservations up until around 5.55pm - depending on availability - (for
The Crystal Palace, and Cinderella's Royal Table or Be Our Guest Restaurant, for example). When you make your dining reservation you will be alerted if you need to purchase a party ticket for the time of your meal. You won't have to leave the restaurant at 6.00pm prompt, but as soon as you have finished your meal you will be escorted from the park - no shopping, or stopping for photos, so please make sure you have done everything before you sit down to eat.
Please come back and visit us if you have any further questions, and you can
send me a direct question if you wish. We are always happy to help you plan your magical vacation to Walt Disney World!
Sue