Hi Caitlin,
I've been looking into something like that for a small dinner party too...don't know how these will help but
Star of Honolulu - they tend to do cruises for over 30 people, i don't know how willing they would be to accommodate less and they are also quite expensive even for the 3 star option
I have been looking into Tiki's Grill and Bar, its totally different and from reviews I have read of them they are really accommodating to requests.
You could also look into something in a hotel, I've looked at hiring the Rainbow patio at the Hilton Hawaiian Village, it isn't too expensive.
Have you also looked into having an outdoor luau?