We recommend taking either the car or person ferry from Red Hook to St. John. Be sure to check times for ferries back to St. Thomas, as the car ferry ends earlier than the people ferry.
Most people will enjoy having a car on island, as there are no Ubers or Lyfts, only taxis and Safaris (open air jeep transport) If you are staying at Emerald Bay Resort, for just the wedding weekend, you won't need a car.