I lucked on to this camper (on craigslist while searching for something else) recently and am proud to start using it for my next dune trip... It's a 7x14 utility trailer, which converts to have a shade, then after snapping/zipping on the sides, turns into a tent/camper. With the AC blowing, it held 60-degrees Saturday night, and takes less than 30 minutes to set up or take down, including the ramp/porch and carpet. The entire setup was built by a retired couple who do engineering and upholstery work for Voyager sailboats, so the quality and design are top notch, and all the canvas stores in a custom made duffle bag.
Let me know what you think, or items you'd add before going to the dunes.