pretty much keep them in a dark box or padded cat carrier...no water. Pack them at night just before leaving, this way they go to sleep quickly as its night, and in the morning all the moving etc doesn't stress them as much. Also don't' feed the day of the move and keep the container out of direct sun but try and keep the temps around 70-75F. Don't leave in the car in direct sun as the car could get too hot and cook them....or freeze them (depending on the exterior temperature). If you stop at a restaurant or hotel, bring them inside with you, in their carrier.
If you stop overnight, you could take it out and set up in a temporary tank to warm up and eat a bit, but probably best to just leave them in the carrier/box till you arrive at your destination. A couple days like this will be fine. Once you are set up in the new place, let them warm up and offer water and food (providing its not too close to lights out)
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PHLdyPayne