Hello, Nicole!
Welcome to the Disney Parks Moms Panel. Thank you for sending in your excellent question! We are here to help you plan all the magical details.
Guests are now allowed to enter the Main Street U.S.A area of Magic Kingdom Park before the park's scheduled opening. There is no specific time given, other than it can be as much as 30 minutes prior to that day's park hours. Buses begin bringing guests from their Walt Disney World® Resort hotels one hour prior to park opening.
I can't think of a better way to start the day than to enter Main Street U.S.A early! I'd stroll through this beautiful area of the park, stop by Main Street Bakery for a coffee (shops and eateries will be open!), and then skip toward Cinderella Castle to catch Mickey & the gang open the park in the all-new welcome show,
Let The Magic Begin. What a fairytale way to start the day!
I hope this helps, Nicole! Please let me know if you have any additional questions. You can reach out to me directly - I'd love to help you plan a perfect day in Magic Kingdom Park.
Faith