Jake,

Call it a "Scavenger Hunt".

Entry fees are $50 worth of canned foods, new clothing, etc. to be given to the regatta's "adopted" charity.

Point-to-point race with scavenger items at each stop.

Sponsors donate items to be used on the scavenger hunt. Flags, coozies, floating keychains, water bottles, etc.

Special prizes for oldest boat, best decorated boat, best dressed crew, etc.

Open it up to canoes/kayaks, daysailers, multis, (depending on distance of the course) which would bring a lot of people who might be tempted to sail multis.

Maybe get the support of the local munipality or parks & recreation district.