Agreed, keep the sand, rock and filter material wet. Keep as much of the water as possible. You can move the fish in cooler with battery powered airstones and they'll be fine. When you get there, add the sand, rock and as much of the original water as possible (try for at least half of it). Let it all settle down and start to clear up and see where you stand. If you have enough water to run the filters, get them going. If not, make up enough new water to get it high enough to run... doesn't have to be all the way full right away. If you add water, let it mix awhile, then reacclimate the fish to the tank. Over the next day or so, make more salt water and top it off.
I'd keep something to check pH and specific gravity handy.