I have 2 suggestions: First is Charley's Carb on NE 32nd St. Their brunch menu is outstanding and the view from this oceanfront restaurant is excellent. It is located on the northern most stop of the water taxi route. This is a chain, however, and not exclusive to Fort Lauderdale (there is one in Cleveland that I have frequented numerous times and often choose when hosting out of town guests).
My other suggestion is the River House Restaurant on SW 3rd Ave. They serve a great brunch in an old mansion on the New River. I had an opportunity to sample their brunch while attending a wedding in Fort Lauderdale.
Both are great settings that make for a very special dining experience. If possible, I would try to make reservations in advance at either place.