Hello Maggie,
Welcome to the Disney Parks Moms Panel and thank you for bringing us your question. It's a Jolly Holiday to be planning your vacation to The Happiest Place on Earth!
The Disneyland Resort is open every day to Guests. We have spent a few Christmas' at The Happiest Place on Earth and they were truly magical. If you plan to visit during the week of Christmas, you will just need to purchase Theme Park Tickets to enter either park. I suggest purchasing Theme Park Hopper Tickets if you plan to attend both Disneyland Park and Disney California Adventure Park in the same day, which is very doable.
The parks are always popular but especially during Holidays at the Disneyland Resort, so I suggest getting to the gates early. If you are a Guest staying at a Disneyland Resort Hotel, be sure to utilize
Extra Magic Hour every day during your hotel stay. With Extra Magic Hour, Guests will be able to enter the parks on select days one full hour before the parks open to the general public to enjoy select attractions, stores, and entertainment.
I hope this helps. If you have any more questions, please write me back, I'd love to help you plan your next pixie dusted vacation.
Wishing you magic!
~ Lynette