Highly unlikely that you will get everything done before December 24th. My oath was on November 13 (Mississauga office) and I needed to be in the States by November 22. I requested that the citizenship certificate be expedited, to which the officer responded that travel is not a valid reason to express mail the citizenship certificate. I told him that I needed to drive my wife for her follow-up appointment. The officer told me to send an explanation in the email, which I did right away - I sent a long email explaining my situation with supporting documents, but guess what.. I still haven't received the citizenship certificate after 10 days. Sorry for the bad news but will suggest rescheduling your trip and not relying on the citizenship certificate to be there on time. Also, factor in the holiday season so IRCC might be short-staffed.