Based on everything I have seen... nothing will post to your WN/RR account until the next statement closes on 1/4 - actually a day or so later. So, you should be just fine spending away now. If you are not going to need the companion pass before mid February, you can wait until after Jan 4th. If you are going to need to pass before that, go ahead an spend away.

My close date is Dec 18th - and I will start using both cards after that statement closes, meaning I will get CP around Jan 18-20th. We actually have a trip for the end of Jan. The "paid" ticket is already booked, but will then add the companion later. With some luck, the flight will not be sold out.