If you don't want to bore people do something outgoing. Have a Hawwiian Lua. Get some inflateable or shiny cardboard palm trees to decorate. You could get some coconut cups or some cups with a Hawwiian print and serve a fruity drink. Then you can pick up some plastic grass skirts or something and have a couple contests like hula dancing, hula hoopong, and whatever else comes to your mind. Your guests can show up in their bathing suit tops and shorts if they're girls and their swimming trunks and a shirt if they're guys. Then just have fun!