As a past Commodore of a 50 boat sailing club we ran into the same thing. How to include the power boaters. We found that in the spring a good draw was to have a pig picking to include a raft up etc. Made sure that any visitors to our marina were given courtesy dockage for the night helped as well. In the fall we would combine a halloween thing to get the kids involved and have an oyster roast and low country boil. Door prizes never hurt. We found that West and others were more than willing to contribute to our cause. Don''t overlook your local Wal-mart as they have great discretion in their budget to help local causes.
Other than that it takes a bunch of work by a few people as you well know.