If the weather isnt to bad i think a hawian party would be gr8!! You could eat hawwian food. hand out cheap grass skirts and lays for fun, have a dance contest, to the limbo, and if you live near the beach have it there. or if not have your own swimming or water party. if the weather is too bad for hawii then go indoors and put on your own 80's party. Sing and listen to 80's music and have your freinds dress up in 80's outfits.
Have a blast!!