Charleston does a lot of weddings, and the fall run is the busy one. If you're a guest rather than the couple, the transport problem is different from what the planning websites cover.
The venues are spread out. Plenty are downtown, but a good share are out on Johns Island, across in Mount Pleasant, or at a plantation property well outside the peninsula. Rideshare downtown is reliable. Rideshare back from a barn on Johns Island at eleven at night is a different proposition.
What guests usually need
Something that seats the group you came with, and something you don't mind parking on grass. The Range Rover covers five people and their bags, which is the common case for a family flying in together. The Fiat 500X covers the cheaper version if there are two of you and downtown parking is the harder problem.
If you're in the wedding party and the couple wants the car in the photographs, that's the Rolls-Royce Ghost, and it books online like everything else on the lot. The luxury page explains how that one works.
Book earlier than you think
Wedding weekends land on the same Saturdays. The fleet is small, so the cars that suit a wedding weekend go first, and they go weeks out rather than days.
Pickup is at 1471 Folly Road, which is close to the downtown and Johns Island venues and a bridge away from Mount Pleasant.