My 5yr daughter's birthday is in February. She has a lot of friends of varying ages(<1 to 10 yr)both girls and boys, so I wanted something fun for everyone. We rented the indoor pool at the local YMCA. I got the invitations in a bottle from Oriental Trading and we invited the whole family. They were encouraged to bring pool toys, swimmies, vests, etc. When the kids arrived at the pool they were each given a sand pail with their name printed on it. In the pail was a lei, a water gun,goggles, luau rubber duckies and a palm tree bottle with straw(all items came from oriental trading). I had bought a bunch of pool toys a the ymca also provided some as well. The kids just played using their goodies in the pool. Parents went in the pool with the younger ones and just to have fun with the olders ones too!.I had luau music playing and set up a Hawaiian hopscotch and limbo on the pool deck for the kids to use as the wanted. For food we ordered pizzas that were delivered poolside. I had a chocolate fountain with tropical fruit , pretzels etc. I also rented a smoothie machine and we had straberry daquaries and homemade pina coladas (Rum was available on the side, the bottle marked with a skull and cross bones) The kids used the palm tree sippy bottle witch cut down on spills. I also got flip flop plastic plates and luau plastic silverware. I've found (especially at oriental trading)reusable plastic novelty cups and plates really don't cost more than the paper character"ones because you use less. people keep track of their cup and dish especially if you put their name on them and send them home as part of the party favor! The cake was a 3-d sandcastle covered in graham crackers crumbs w/ white chocolate sea shells around it. Other than an inflatable palm tree there was very little in the way of decorations or structure. We set out all the food at the beginning and people would take breaks as they needed. Everyside was seved on the pool side so messes were not a problem as the deck was just hosed off whem we were done. Kids who got cold would get out have a snack play a few games