One tunnel calendar, or you will double-book a coach
The single most common failure in this business is a coach arriving for a 4pm private lesson to find a family already in the tunnel with a bucket of balls. It happens because lesson scheduling and cage rental were set up as separate systems, and nothing in either one knows the other exists.
The fix is structural rather than procedural: the tunnel is the resource, and both lessons and rentals consume it. When a coach is booked into tunnel 2, that tunnel is not available to rent for that hour, and no amount of front-desk vigilance is required to keep it that way. Any facility running more than two coaches should treat this as a hard requirement.