As for my performance, I will add New Year's Day elements to my show. BUT! The foundation of my show will remain the same.
When people book a magician for the New Year's Day party, this does not mean that he/she will only do holiday related magic tricks. When booking a singer, the customers do not mean that all her/his songs will be dedicated to the New Year's Day. Dancers, too, will not dance only New Year's Day or X-mas dances. Keep this in mind, do not be too focused on the holiday theme. You can introduce some elements of the holiday but you should not do completely Christmassy.