Hi Amanda! Thanks for visiting planDisney.
It is possible for a Disneyland Park or Disney California Adventure Park to be full on a popular day and entry to be paused. Although, with the introduction of theme park reservations, this has rarely and only briefly happened. Christmas Day is a popular time to visit, so I understand your concern.
You might consider heading over to a nearby Downtown Disney District location to eat or select one of the fabulous
dining choices in the
Disneyland Resort Hotels. They're close and there's a wide variety of choices and immersive experiences to explore. After you're finished with your meal, you are free to reenter the parks with your theme park reservation and
admission ticket so long as the park isn't full. Should you return and find that entry has been temporarily closed, in all likelihood it will be reopened after enough Guests have exited.
There are also great dining choices inside the parks. Some might even feature a special holiday meal. Regardless of where you decide to dine, you'll find the parks full to bursting with magic during the
Holidays at the Disneyland Resort. Festive decor, merchandise, menu items, and Attractions transformed by holiday overlays will dazzle and entertainment, parades, and fireworks will get you in the spirit.
I hope this helps!
Elizabeth