Public Witness is a small website for your congregation. Every place you set up a cart gets a page of its own, and a publisher opens it right at the cart: directions, photos of where to park and where the cart goes, and the permission that covers the place. It is free, and publishers need nothing but their phone.
Four parts, in the order they need them.
The brother who looks after the carts records each location once: a photo, the steps, a few details, and any permission. Each cart gets a printed code. When a cart moves, its code keeps working, and the site shows you what is still missing.