Good Day, Mister Rawles,
Thank you as always for the good work you do. Regarding a late convoy out of Dodge I have this to add. I can only imagine that if you have to stop for a tyre change then you will become powerful goblin magnet. Needless to say it will not be a good time to be breaking rusty wheel bolts free with an old tyre iron. Thusly it's imperative that your wheels have been previously removed and meticulously reinstalled prior to your leaving. Your spares (yes, plural per vehicle) should be mounted to the outside of your vehicles. On a roof rack or tailgate would be the traditional approach.
The previously mentioned maintenance vehicle running second to last in the pack will want to be equipped with a professional grade jack capable of lifting both the highest and lowest cars in your convoy, and a well charged cordless impact driver with spare batteries and labeled sockets for each vehicle is imperative.
You want to to be thinking NASCAR pit crew, not roadside assist. Any observers will have less time to organise and will also determine that you're going to be a tougher nut to crack than the usual TEOTWAWKI tourists.