I did it from Alaska to NY in wintertime which took 10 days. I left with 23 and ended up with 4
. We had an issue with an open back window hen it was -40 and my fish were right next to the window.
As long as they stay warm, they should be OK since you will be able to check on them at rest stops and such. I kept mine in their cups and ended up having to hold the survivors in front of the heater under several blankets due to the extreme cold in Alaska and the Yukon. However, i dont think that will be an issue for you this time of year.
Bring an eye dropper or something to take out old water and replace it with new water. I had all my fish stuff in a 2 gallon storage container and on the nights we did spend in a hotel, I let each of them out and let them swim around in it for about an hour each and then recupped them.
I also used amquel plus and krodon fish protector as I was told both were good to use for long distance shipping of fish. not sure if it really makes a difference but its worth a shot
did i mention I also had a dog and a chinchilla on this trip..