Redfish Grill is casual and good food. It is in the Brennan family who own a number of restaurants in New Orleans.
Casual, good, and often with a line, is Acme Oyster
They have a webcam you can watch.
One place that usually piles the food on is Deanie's. They have a location in the French Quarter.
All are within a block or two of each other. You could check them out and decide what might be best for you.
There are LOTS of good, casual restaurants to choose from.