It will be pretty busy but keep in mind that SeaWorld parks handle crowds well because of how many people fit into the theater. The park has extended hours that night and its early in the Christmas Celebration shows so a lot of people will be wanting to see that and how pretty the park is for Christmas. If rides are your thing you will probably want to get quick queue but if you are not a ride person no need for it. For the shows for a good seat arrive at least 30 mins early. Hope this helps