Hi there, Dana!
Welcome to the Disney Parks Moms Panel. I can't wait for your family to make magical memories at the Happiest Place on Earth. I think it's wonderful your little one has already expressed interest in what she wants to wear on your vacation. Costumes are allowed to be worn in the parks as long as you are under 14 years old. Check out the
dress code policy online to make sure her costume follows these guidelines. If her costume was purchased at a Disney Store, there's a pretty good chance it will be fine to wear in the parks.
If you will be visiting the Disneyland Resort after November 9, 2018, you are in for a real treat as the
holiday season will be in full swing. You'll find festive fun around every corner. I just love the Christmas-inspired treats you can eat in both Disneyland Park and Disney California Adventure Park as well as limited-time holiday-themed attractions. You won't want to miss Haunted Mansion Holiday, "it's a small world" Holiday, Mater's Jingle Jamboree, and Luigi's Joy to the Whirl. Another highlight is seeing Sleeping Beauty Castle dazzle as a part of its winter transformation.
I can't wait for your vacation, and please return if you have any other questions as your trip approaches. Have a magical day!
-Jennifer