I've traveled cross-country with my animals several times....and am about to do so again in a couple of weeks. It CAN be done....but a lot of common sense needs to come into play.
Were I in your shoes, this is what I would do:
First....try to find someone trustworthy to care for the snakes for a few days and then ship them to me once I'm settled in. (As has already been suggested) That would be ideal....but not always possible.
Failing that, I would do this:
Find an appropriate sized "shipping" box for each snake. You won't actually be shipping in these boxes, but the snakes will be staying in them for a few days, so they need to be properly padded, insulated and not air-tight....just as if you were going to ship.
I would get a pillowcase for each snake to use as a "snake bag."
Lastly...get a small rubbermaid container for each snake (as small as you can get away with, but still give the snake room to move around a bit and have a water bowl).
1. Pack each snake into its own bag....tie the top of the bag into a knot AND use a zip-tie to tie the neck of the bag very securely. You don't want to take any chances of the snake getting out of the bag unless you take it out.
2. Make sure your "shipping" boxes are both insulated and padded...place a bag in each box....tape the boxes shut and mark them VERY clearly exactly what is in each one.
3. Place them in a secure place on the floor of your car. You don't want them in a drafty place like right in front of an air vent....nor do you want them anyplace where the sun can shine on them. You also don't want them someplace where they can fall or get banged around in the event of an emergency slam of the breaks.
4. When you stop to spend the night somewhere...bring them into the room with you. They can stay overnight in the "shipping" boxes...but on the second night, I would put them into the rubbermaid containers with a little water and newspaper substrate. Make sure the lids are VERY secure!!
5. Pack and repeat until you reach your destination.
Use the largest rubbermaid to hold the smaller ones...as well as these other supplies:
1. Water bowls
2. Extra zip-ties
3. Extra pillow cases in case they pee or poop in one
4. UTH's and controllers, if you can, for warming tubs in the hotel room.
5. Newspaper
6. Tape for re-taping the travel boxes.
7. Clamps and/or weights to help secure rubbermaid lids.
COMMON SENSE things to Remember:
1. Don't feed any animals for at least a week before you begin this journey. It won't hurt any of them to miss a few meals. Better that than to risk a regurge along the way.
2. NEVER EVER leave the animals unattended in the car on a warm or sunny day. During the day, all meals should be taken via drive-thrus. Restroom breaks should be done very quickly. Run in and use the rest room and get right back out to your car. If you have a person traveling with you, it's better 'cause one person can always stay with the animals to make sure the car isn't getting too hot. If you're alone, don't take more than five minutes at a stop.
After dark, you can stop for a decent sit-down meal or browse a store for snacks....but not during the daytime.
3. If you can't manage to heat the tubs overnight....just keep your hotel room temps set warmer than you might usually. The animals should be fine, so long as they don't get too cold.
4. Carry a digital thermometer with you and keep it on the floor with the boxes in your car so you can see how hot it gets there....and in the hotel room, you can tell how cool you make it at night. Don't let it get below 75 at night and you should be fine.
5. SECURE SECURE SECURE! Make sure bags and boxes are always secure. And make sure the tub lids are secure when the snakes are in there. Never have more than one snake out at a time while making those transitions.
.............. I'm sure I'm forgetting something...I may come back and add more as I think of it...or others may have additional thoughts or suggestions. This is just what I would do if I had to make such a long drive with my snakes. So far, the longest journeys I've had to do have been two day drives....but this is how I would plan for 4+ days.