I would call MS on Monday, as you should have received them by now. Even if they've gotten lost in the mail and have to be re-mailed, you'll still have plenty of time to get the new ones before your trip. Have a great trip and safe travels!
I always write a reminder to myself to call about a month before arrival date, just in case the tags don't come. So far, I have never had to call; they've always arrived anywhere from 6 weeks, up to the month out mark.
We will be arriving on January 24th and have not received ours yet. I need to call this week for something else, so I will mention it then if we haven't received them.