I had always thought of seersucker as primarily a daytime fabric, and have avoided wearing it to evening events for that reason. That being said, (1) I think you get more leeway with a jacket than a suit, (2) 6:00, although technically "evening" is, of course, broad daylight in the summer in Florida, and (3) there's nothing incompatible between the setting and seersucker.
All in all, I wouldn't classify this as an etiquette issue. In the days and places when dinner meant dinner jackets, I suppose it would have been, but these are not those days nor places. But I do think, as a practical matter, that seersucker looks better in daylight than at night. But in the sort of setting Oldsport describes, it's likely to work just fine and fit the occasion well.
