Where to buy tasteful luau dresses for 5 year old twin granddaughters?

My wife and I will be taking out twin 5 year old granddaughters to Maui next year and would like to outfit them appropriately. We don't want to dress them in tacky touristy clothing, but rather simple hawaiian clothing that would be appropriate. Can anyone suggest where one might shop for such clothing and possible suggest something appropriate for luau's etc.?