Well you have 6 girls in total, you should make your own leis. You could get real orchids (sorta pricy) or you could jst get artifical flowers. I loved makin my own lei when I was in Hawaii. I went to a luau too, there were activities like make your own lei, and head band, but if you dont like in a tropical place i dont think you can get the right stuff to make them...I'm from Canada so I dont know exactly what they used. You could possibly do a search though. You could learn how to hula etc.. make up your own dance, burn some hawaiian music from the net or buy a CD or tape. Get some grass skirts to wear. Do the limbo etc. I'm trying to think what else you could do.. Im out of ideas, but if I come up with more Ill post them!
I hope I helped you!