The best wedding shuttle plan is the one your guests never have to think about.
Start with headcount and hotel blocks. If guests are staying at one or two room-blocked hotels, a shuttle loop between those hotels and the venue is usually more efficient than individual car service. A single 30- to 40-passenger coach can typically replace 15 to 20 rideshare trips, which matters both for cost and for making sure everyone arrives together instead of trickling in during the processional.
Timing is where most shuttle plans break down. Build the schedule backward from the ceremony start time: guests should be seated 20 to 30 minutes before the processional, which means the last shuttle needs to depart the hotel with enough buffer for traffic, loading, and a walk from the drop-off point. Most couples underestimate loading time — plan on 10 to 15 minutes to load a full coach, not the two or three minutes it takes to board a car.
For the reception, a continuous loop (rather than one fixed pickup time) gives guests flexibility to leave when they are ready instead of being stuck until a single scheduled departure.