My daughter asked for a Hawaiian Luau for her 8th birthday. We had fun planning the meal, thinking back to any Polynesian-type meal we'd experienced in the past, including inspiration from Disney's "Spirit of Aloha" dinner.
For the food, I made a teriyaki chicken, with vegetables and mashed potatoes (not Hawaiian, but my daughter's favorite side dish). We had pineapple and other fruit, a salad with Polynesian dressing (home-made), and coconut milk shakes (with paper umbrellas).
The cake was a palm tree - I used cupcakes to form the shape, then iced them (second layer) together, so that the design was unified and didn't look too much like separate pieces. Once the second icing layer was on, I took green decorating icing and drew the palm leaves.
I used paper lanterns in various places (above kitchen counters, where food was served, above the party room, above the entryway). I put an island scene on the wall behind the birthday table, and had lots of bright-colored flowers and ribbons on the tables to match the plates I bought. I borrowed some silk trees to help give the room and more "outdoor" feel.
I also ordered this luau-girl poster from Birthday Express, where the face is cut out, and each guest holds it up to his face. They had fun doing that.
I found several Hawaiian-themed serving trays and bowls at the dollar store.
For party favors, each guest received a flower bracelet, flower flip-flop clips, a lei, and some candy. I found coconut cups with straws and grass skirts at the dollar store, and had one for each guest to take home, as well.
We played Hawaiian music and had a limbo contest. Everyone was dressed for a luau.