If you are travelling as part of group, you would naturally want to book all cars together. When making the reservation, first of all complete the journey details and after that your personal information. Underneath your details you will find "Add another vehicle". If you click on this button, you can submit the details of the second vehicle. The maximum number of cars you can book for is nine. Every car will get its own reservation number, therefore there will never be two cars mentioned on one confirmation email.
Please note: are you submitting a different name and email address for the second car? Then the confirmation email will be sent to the email address you submitted for the second car.
Not every parking provider has fixed parking spaces, in that case, you will select your own spot. This means that, when travelling in a group, you will be able to park the cars next to each other, permitting that there is space to do so.