Build a crate or find an old cage or dog crate. Throw that plus your bag of feed and some water in your vehicle. Do it now, just in case! If it comes down to it, I'd think turning them loose would be the best thing to do. Good luck!
You know what...they could all go in one box if they had to. You do what you have to do until you can do something else!
A clothes hamper with something on the top for a lid...a plastic trash can with wire over the top for a lid...plastic crates...if all else fails...just put the babies in the box and the hens right into the car. Yeah...they'll poop in it but it can be cleaned...