You use the Aulani ones. All popcorn buckets are good for the length of your stay. People bring back older ones, but technically, you are supposed to buy a new one every trip. And you most definitely are not supposed to use one from WDW. The parks and Aulani are 2 different entities. Even though they are both owned by the same parent company(Disney), they are run separately. Just like you can't use your WDW AP discounts at DL. They run things separately.