Frank:
To echo what the others have said, for the guys at dinner nice slacks/shirt and shoes, for the ladies a nice dress or shirt/skirt. Depends on the time of year, and the restaurant your going to be in for the evening. The buffet, casual. The other two, when we were there last May, was dress-up. Think of what you would wear going out on a "date" to a nice restaurant, that is what you should wear.. NO JACKET / TIE !!! for goodness sake your on vacation at a nudist resort

.
My wife always wears a very nice elegant yet sexy dinner dress without being too revealing (imagination is a good thing -

), even though everyone just saw her 5 mins ago naked

., with the exception of the first night we ever went there (been 3 times) she wore a skirt/shirt - still it was very nice, but she felt more comfortable wearing dresses the rest of our 1st time there and always on the other trips, not to say she does not pack skirts and shirts.
Myself - The first visit, first night I had a nice pair of docker short pants, a collared shirt, and sandals. Since that night, I have had slacks and nice shirts. DON'T forget to pack shoes !!
NOTE - The first night we were ever there we went to the buffet, basically wearing what we wore on the plane. We had arrived about 5pm and we very hungry. REMEMBER - WE ALL WERE NEWBIES AT ONE POINT IN TIME !!!So, basically as you can guess, there is no WRONG way. Last time we were there we noticed a guy wearing a tank top all the time, even at dinner, but we never saw him other than in the buffet either. His attire was perfectly fine.
For us, it is our get away from the kids, be adults, have a great time together get away. We enjoy dressing up for dinner and think of it as a "date", we have been married 25+ years. In the real world, we rarely get to go out on "dates", so we treat this as something special to us.
*** 3am PIZZA is the best eaten naked gazing at the stars !!
Hope this helps in some way,
Gordon