A luau sounds like a treat for all the guests! We thought about doing one too for our welcome dinner, but it was just too spendy at $100/head. We looked at a bunch of other ideas to try to keep it friendly on the pocket book (under $25/head) and while still doing it nice.
After looking into options in South Maui:
Capische -- broke the bank
Da Kitchen -- fantastic local grinds, but way too ghetto and hole-in-the-wall
BBQ on the beach -- too risky not getting a good spot with other tourtists/visitors
We finally settled on doing a casual BBQ at our private rented condo for a more economical and intimate option. We had to search high and low for a nice condo with BBQ and grounds to accomodate our party of 30, but we found several in Wailea and Makena. We're planning to get drinks and alcohol from Costco (yes, they sell alcohol & wine!!) and platters of BBQ and pupus from Da Kitchen (in Kihei). Fun and hits all our criteria.