When I made ressies for Tchoup Chop, the reservationist told me "resort casual" with no sleeveless (tank or muscle) shirs for men. I think people are probably pretty casual, but I may dress up a bit, just because it is just hubby and me.
I have seen people dine in a suit and tie or in khaki's and a golf polo and both have been just fine. Women have been in cocktail dresses as well as dress capri's and a nice blouse. I think everything goes with the exception of shorts/jeans and tees.