So far, my plan for "camping" comfort is a cheapo inflatable pool float. I'll blow it up in my car, bring it to the queue and use it for whatever sleep I can get, then deflate it and either toss it in the trash or pack it in my backpack. I will have a car, but don't want to carry a chair back to it. Solid chance I skip it altogether, though, and just bring an old beach towel.
Honestly, my primary concern about spending QT with the concrete is fire ants: I'm VERY allergic to them. They don't seem to hang out on smooth asphalt much, but cracks in sidewalks are prime fire ant real estate. If you see someone creating some kind of DEET (is that even a threat to fire ants?! I need to do some research...) and Mylar blanket blockade around her spot in line, that'll probably be me lol!