How about a tourney where anything you catch is worth points. I.E. Bass are 8/10pts. Bluegills 1 pt. Carp 1pt. over 24" 4pts. Catfish 4pts. etc. you get the idea.
The Cinti. Anglers Club have been doing this for over 30 years. Great fun and you would be surprised where these guy's can catch fish. All fish have a min. length to check in 7" Bluegill. 8" Crappie etc or the prevailing lake/river rules.

Dave.