Welcome to the Disney Parks Moms Panel, Katie!
I'm thrilled you've stopped by with your great Walt Disney World Resort planning question and hope you are having a wonderful time arranging your magical vacation. I'm going to assume for this question you are talking about Magic Kingdom Park, so that is what my answer will reflect. If not, please send me another question so I am able to give you the right information.
Beginning in January, Disney changed the way Magic Kingdom opened and now all Guests are allowed to enter the park prior to the scheduled opening time. This early entry may begin an hour prior to the park opening, so depending on where your early morning Advanced Dining Reservation is, earlier admission may not be needed. If you have reservations at Be Our Guest or Cinderella's Royal Table, there are Cast Members near the "hub" at the castle end of Main Street, U.S.A., who will let you through shortly before your scheduled reservation arrival time.
Happy planning, Katie, and please let us know if there is anything else we are able to assist you with.
Magical Wishes,
Lauren