Describe in detail the downriver race. I'm a III boater, but didn't bother coming out (with the associated scheduling/adjustment of family issues) because it was described very casually, and unless you've boated those runs a lot, you don't know.
Also, I'd make the (or a seperate) downriver race that ruyns primarily on class I/II - There are a quite of hardcore downriver paddlers looking for a "race" that doesn't involve class IV drops and super hardcore whitewater. These guys have a lot of unique, interesting boats that most folks on the buzz and elsewhere have never seen, but you won't get them out unless it's a race of at least 3 miles and the rapids are all III/II or less. Obviously, not really a whitewater/boaterX race, but if you are celebrating the river, you might try get all the river folk out.