I think either of your two new scenarios is better than trying to squeeze three islands into eight days. Personally I thought the GW was vastly better than the Hilton Waikoloa but I do love the Big Island. If you choose option 1 (six nights at GW) what would you do for the other two nights? Can you find a way to get another 15K HH points? If so you could stretch it to eight nights with the 5th night free on point stays.