I've not been to a luau on Maui but if you're staying at a hotel or resort they may in fact have a tour desk that can offer suggestions and possibly discount coupons for a local luau that they have a contract with.

Also, check the hotel website for activities in the area - they may list one on their site. When you arrive at the airport pick a copy of "This Week" in baggage claim, as well as other tour brochures, there are often luau offering in these publications and occasionally discount coupons.

Don't be in a rush to get out of the airport, spent some time looking thru the racks of tourist fliers. You may find something exciting to do that you'd never thought of.