Can I release our iOS app on Christmas iTunes Connect says:


  Make sure your apps are up-to-date and ready for the winter holidays. New apps and app updates will not be accepted December 23 to 27 (Pacific Time), so any releases should be submitted, approved, and scheduled in advance. Other iTunes Connect and developer account features will remain available.


If I have the app already approved by Apple before the deadline, can I still release it on Christmas if I use the "manual release" or "automatically release no later than" option?
This could be a question that no-one here can answer unless they've previously tried to do this over the Christmas period, so my suggestion would be to call the Apple Developer Program Support number for your country. 

To find the number, refer to: https://developer.apple.com/contact/phone/

I just feel this is the best way for you to get a definitive answer.