Welcome to the forum Thomosam.
I am going to try get this time line right first.
You pick up the tank and fish, drive an hour and a half, hold everything overnight and then drive 4 1/2 hours to get to your destination. Then you can figure at least an hour to set the tank in place and fill it with water so I figure 6 to 8 hours before the fish have a new tank to live in.
If you pick up the fish and have a suitable clean bucket, place the fish into it. Empty the tank and move the gravel into another plastic bucket along with the filter and some small amount of water. Now you can move the tank and the two buckets into the vehicle. Make your drive and take the buckets into your room to keep them warm overnight. Be certain that the tank is dry or that you can prevent it freezing. Ice can break glass very easily and will destroy the seals on a tank. If you must, carry the empty tank to the room too. In the morning, take care of breakfast then load everything into the car and make the trip home. The fish and filter should really travel in the passenger compartment so that you can keep them warm easily. Once you arrive, set up and fill the tank, add the filter and start everything up. Next up is a drip acclimation on the new fish. They have just been asked to completely change the water source so they will need some time to become acclimated while more and more of the new water is mixed into the water that they are traveling in. When most of the water in the bucket is from the new setup, you can move the fish into the tank water.
Do not worry too much about the temperature swing in the unheated bucket overnight. The mollies won't care as long as the air is warm enough for people and most cichlids can take a bit lower temperature for a day.