I ship shrimp all over the continental U.S. My shipments usually reach their destination by three days, but I know they can last longer.
Here's how I package my shrimp.
Use Kordon breath bags, filled with a minimum of three times the volume of occupant, in water. I place boiled yarn in the bag, to provide the invertebrate with something to hold on to (reduces stress from constant swimming).
I then put the bag in an foam insulated cardboard box, filled with ripped newspaper, so that the bag can not move.
Do NOT feed, or put food into the bag with the crayfish. It will do fine without food for that amount of time. Food will only increase the nitrate and ammonia levels, either by rotting, or by being pooped out. Since the bag is smooth, there will be next to no bacteria present to eliminate the toxins, and can increase stress by fouling the water.
If Big Al's does not have Kordon breath bags, order some online before you go. I always by the Kordon brand, and have had excellent luck with them. In all of my shipments, none have burst. And make sure that you get a large enough bag, and I would get more than one. You should double bag a crayfish, and you never now when you might need one. They're very handy.
Good luck