I just moved down from Washington DC 1684 miles in 4 days. The temp outside when we left was in the uper 30s. I understand the dillem you are going through. All I can tell you is how I did it. And hope it helps.

I had a 50 gal reef tank. So what I did was ought a 24G nano cube (Which is now a mini reef set up in the living room). Put an inverter in the car to run the filter, lights, and 2 300W heaters. We sealed the top of the tank with reynolds press and stick plastic wrap. When we stopped at night I ran an extension cord to the hotel room, so I wouldn't run down the battery. I transfered everything except some of the sand and live rock into the nano. That was transfered into 5 gal buckets. We made the trip. and the temp in the tank worried me. On some nights the temp dropped to 69 f. But over all we made the trip and didn't loose anything. We did have some minor water leaking, but over 1600 miles I can't complain.

I doubt that you are making this long of a trip, but hopefully you can take pieces from my trip to help you out.

Oh and those air pumps talked about before, they are in the fishing area of Wal-Mart. They are used in minnow buckets to keep them alive.