It depends on the system that's consuming OSM data. It's umlikely that neither school bus or delivery drivers use purely OpenStreetMap for their routing data, if at all. The OSM routing app I use will ask me something like "It seems like the only way to access your destination is via a private road. Allow use of it?" - I would think that a delivery driver's navigation would allow something smart like that, but really it just depends on what specifically they're using.

Ultimately nothing you do on OSM (or any other map data for that matter) is going to physically prevent someone from using your driveway as a turnaround. Many people, myself included, will ignore gps instructions when it seems necessary.

Hope that makes sense!