We've had multiple passes before without problem. This year (January 3) when we checked in we received our parking pass at the security gate when we drove in at the BWV. We always received them at the front desk in the past. This was our first time with a car in a while, so maybe this changed several years ago. Still, you may not have to worry as when you tell the gate attendant that you are checking in and give your last name, he may have the passes right there. You can say - these two cars are together. Enjoy your trip!
For that matter, you can even ask for extras for your own car. I have only done so 2x (I think) and they never even questioned me why. I lost two of them with a convertable one trip and it was a hassle so I try to think ahead now.