Wow, I like the cooler idea. I just moved 6 tanks. It was quite the undertaking. That should make you feel better
I emptied the big tanks completely because I didn't want them to get broken. I put the substrate and plants in a new/rinsed plastic storage container with enough of the tank water to keep everything submerged. I think you can do this in your thirty, but I would bring the water level as low as possible. If it torques and breaks, you have a bigger problem on your hands, so choose wisely. I left substrate and about 2 inches of water in my thirty, but it is a quality tank and not at all flimsy. I put my fish in gallon sized ziplocks, but I like the cooler idea too. I left the fish in until the water was way down. Took them out. Emptied the tank as fast as I could, drove everything to the new location, replaced the substrate, filled it up monitoring the temp, so I could float the fish immediately. I use Prime, and Stability to boost the bacteria. I also used Stress Coat. DO NOT change your filter as logic may dictate to a newbie. Keep it wet and get it going in the new surroundings asap. Acclimate the fish to the temp, check the water parameters like ph to make sure there isn't a big change. If there is, acclimate slowly by adding a little new water at a time to their current water every 15 min or so. The bigger the difference, the longer this should take, a few hours at worst. Keep testing their water and the new water until they match. I even had some sick fish in a hospital tank and didn't lose any of them, so it worked. I monitored the tanks pretty closely after. Give it enough time and attention and you should be fine. In 10 days, repeat. You may get cloudy water. Don't get too bent out of shape and start messing with anything until you have accomplished the second, final move. Best of luck