Oh! I donn't see in your original post where you mention coming back to the same beach. How about something like a weekend-long "Macho Man" style race where the racers camp-out overnight. Say from Dunedin to Egmont Key or Anna Maria Island one day, and back the next? I'm sure I could talk the Beach-House Restaurant into providing us with beach access to hold the boats overnight. They've sponsored catamaran regattas many times before, usually a combination of buoy racing and a short distance race (up to the Sandbar Restaurant and back, or up around Egmont Key and back) over the course of a weekend.
The idea of spending a week doing distance racing and ending up back at the beach you started from is also very enticing.