The “official call” for the event says this:

Join us for a Southern dinner buffet, cash bar, and a taste of South Carolina culture, including:
Carolina Shag demonstration
Sweetgrass basketweaving
Gullah storyteller and singers

Wikipedia says this:

Celebrating Gullah culture

Over the years, the Gullahs have attracted many historians, linguists, folklorists, and anthropologists interested in their rich cultural heritage. Many academic books on that subject have been published. The Gullah have also become a symbol of cultural pride for blacks throughout the United States and a subject of general interest in the media. This has given rise to countless newspaper and magazine articles, documentary films, and children’s books on Gullah culture, and to a number of popular novels set in the Gullah region.

Gullah people now organize cultural festivals every year in towns up and down the Lowcountry. Hilton Head Island, South Carolina, for instance, hosts a “Gullah Celebration” in February. It includes “De Aarts ob We People” show; the “Ol’ Fashioned Gullah Breakfast”; “National Freedom Day,” the “Gullah Film Fest”, “A Taste of Gullah” food and entertainment, a “Celebration of Lowcountry Authors and Books,” an “Arts, Crafts & Food Expo,” and “De Gullah Playhouse.” Beaufort, South Carolina hosts the oldest and the largest celebration “The Original Gullah Festival” in May, and nearby Penn Center on St. Helena Island, South Carolina holds “Heritage Days” in November. Other Gullah festivals are celebrated on James Island, South Carolina and Sapelo Island, Georgia.

…and a whole lot more. So, not slaves, but still incredibly tone deaf about how it looks. The official call also says this:

Please wear cocktail attire — this is your chance to dress up a bit!

Heh.