Coming from a 16 year old guy I would really have to say Polynesian! It has been great and lots of guys and girls my age were there Hmm, if money is not a prob stay concierge, I do every two or three times, it is great! For your siblings there is tons to do, and the beach is right there. They also might like staying at AKL but I have heard there are lots of bugs there that you cannot see but leave bites If ya need more info lemme know!
This is the mother in me coming out...are you 16 and going alone with your siblings? If so, hotels do not allow those under the age of 18 to check-in. If you are going to do this and WDW allows it, I would stay in a monorail resort.