Adults can get EC numbers online, but if you want to enroll family members that are under-18, you have to complete the household form and then BA will assign them EC numbers. When I did this a while back, I put a note on the form, and someone from BA called me back with the new EC account numbers--and it was only a matter of days when they did so.

In any case, I don't think that you need to have the account numbers filled out at the time of the test drive. You should be able to fill them in later, and get the completed forms in the mail by 3/31.

On a related note, I suspect that Jaguar dealers might not allow test drives for persons under 18, though I didn't research this. Cats and fictional persons would also be questionable.