Our group of 4 did this excursion after we disembarked from FOS in October. It did not include a trip to the park's visitor center. This is a private airboat tour company and the excursion starts and ends at their tourist center.
The airboat ride was fairly short, 45 to 60 minutes if I recall correctly, but enjoyable. The excursion also included a short talk by one of the tour company's staff on the Everglades.