Combine cornmeal and 2 tablespoons Creole seasoning. Dredge oysters in cornmeal mixture.
Pour oil to a depth of 1 inch into a Dutch oven; heat to 375°.
Fry oysters, in 3 batches, 3 to 4 minutes or until golden. Drain oysters on paper towels.
Stir together 1/2 cup mayonnaise, vinegar, and mustard. Stir in cabbage; set slaw aside.
Stir together remaining 1/2 cup mayonnaise, ketchup, and next 3 ingredients in a small bowl.
Spread cut sides of French bread rolls with ketchup mixture; place oysters and slaw evenly on bottom halves of each roll. Cover with tops. Serve po'boys immediately. Garnish, if desired.