In any event, your emerald club number is linked to your DL so it will come up when the agent keys in your DL number. I would ask someone out in the aisle when you get there. You might be able to hop in a car and get it sorted at the exit booth, or they may direct you to the counter where the agent will print your contract and then you'll go out to choose a car which will be assigned by the exit agent (done this a couple times). Either way, you should still get choice of vehicle though the rental process may take a few minutes longer than booking directly.