Well they are going to have to come out. Good thing is that you dont have to travel with them. Depending on the size of your fish ,get a bucket or rubbermaid container that will hold them, drop an airstone in there and make sure you have a a heater in there as the temperature buffer will be small due to the small volume of water. If you can fit a HOB that would be great too. Add some plastic plants to float on top to make them feel more secure and to keep them from jumping. COVER the tank with something, fish like to jump if startled or scared. Dont feed them the night before or that day to keep your water from being fouled.
Switch out your tanks.
I had to move 3 tanks and a household last year in the middle of chicago winter, and the fish stayed in containers for 6 hours, untill the move was complete. Not a single loss.
HTH