Not having been, I don't know for sure, but I believe the second seating tends to be dressier in most of the restaurants than the first. And I'd guess that the "adults" rotation will be dressier than the "kids" rotation.
Wear what you are comfortable with and let your wife wear what she is comfortable with. As Dabney said, a lot of women think dressing up is fun. Of course, marital harmony and your chances of getting lucky might improve if she thinks you make a really good looking couple with her in her dress and you in your suit.
I'm bringing something that verges on formal for that night, I have NO idea what my husband will pack - nor do I care, except I've informed him we are requested not to wear shorts or jeans (he tends to dress pretty snappy, I'm not married to a guy that wears a lot of jeans and shorts anyway).