For my 11th birthday party, i decided to have a luau! my birthday is in feburary, but i waited until may.  for the invitations, i cut out little palm trees and put them on the front, with a little sun next to it. on the inside, on the left side, if you're not going to use it, draw/cut out a little hawaien flower. then on the other side write the RSVP, date, time, adress, and any other needed information. you should start planning at least 10 days before the party. Make sure you have a list of guests, a checklist of materials, a schedule for the party, and a list to write down presents for thank you letters. I decided to have my birthday party on a saturday from 2:00-4:30. that way we wouldnt have to do lunch or dinner.  when the guest arrive, we "crown" each person with a lei. While everyone is waiting for the guests to arrive, you may want to have a game set out, or something like that. once everyone is there, they might be thirsty, so a smoothie would be very refreshing and apropriate. let them choose the fruit to put in. pineapple,kiwi, or other tropical fruit is recomended. you can also put those little umbrellas in each drink. once everyone has arrived and had their drink, its time to start the party a good "get you going" game is a water balloon toss. make sure that everyone has a towel and an extra pair of clothes. make sure it is warm out! then, you might want to have fun turning a classic game into a hawaien game, like turning bingo into shell or something and use shells as the chips. for prizes, you may want little fish (real) or squirt fish(not real) or bubble makers, tiki sculptures, pretty shells, a great hawaien game is the LIMBO! its wonderful and hawaien, and lots of fun. again, you may want to consider prizes. once again, turning a classic into a hawaien version could be pin the tail on the donkey/pin the coconut onto the tree a great game thats appropriate is "search in the sand" where a little sandboxis filled up with sand, and under all the sand scattered around are little sea shells, or other tiny prizes.  get your groove on! let everyone make their own hawaien skirts out of raffia material then have a dance contest or freeze dance ect.  you may also want to tape everyone and send everyone a copy as a memory. then, once people have the hang of hula, you might want to have a hula hoop contest, which is lots of fun! then, at the end of the party, open the presents, hit the pinata, and eat the cake! once it is time to go home, give everyone their goody bags, ect. later, you may want to give out thank you cards. it works best if they are in the same style as your invitations.