We usually rent a "cabin" which is a double wide trailer that is within walking distance of the dune lot. Its pretty clean, has 6 beds, 2 couches and a pull out sofa bed. It rents for $150 a night. It can easily accomodate two 20' trailers in the front and another in the back. Its very safe, just throw a lock around your quad and no worries. There's a fire ring in the back for camp fires. Hit me up if you want the contact info.
Oh also don't bother getting flags in advance, SL requires a special height just buy them there.