The Gorge Camping Question

Going to the Gorge for the first time this May for Illenium and have a question about the camping! I have 6 people staying at one campsite, but my car only fits 5 so the last person is coming with another group. I saw that it says all people staying at a campsite has to be there when we check in, so I'm wondering how this would work? Would this last person have to walk through the line up or can they just squish into the car for the line? Do I have to get a bigger car?