The CRBA embassy BsAs page says this
Delivery of CRBAs
All documents are printed in the U.S. and then delivered via DHL, typically within 20 days. Applicants must visit the DHL branch at Avda. Cabildo 1209, Buenos Aires, to arrange payment. We strongly recommend visiting DHL before appointments in order to obtain an airway bill sheet with a tracking number. Visiting DHL after your appointment may result in delays.
So I'm banking on the idea that it takes less than 20 days after your appointment to get both CRBA and passport, If you have your appointment on the 25th and leave December 21 you might get the CRBA and passport around the 15th with a week to spare. I hope all goes well for both you and I. I really want to spend my babies first Christmas with her American grandparents and uncles and aunt.