Do you have the SPG Amex? Since your trip is not until September you could rack up a good amount of spending on the card to make up a good chunk of the difference. If you don't have the card, a sign on bonus could even make up a lot of the difference. Best sign-on bonuses have been 30K points - but only 10K of it is instant and guaranteed to be there in time. Not sure if you're traveling with a significant other who could also apply?
I think there is more than one Westin in Maui but I stayed in one that was nice - it was great because it was a timeshare and had a kitchenette which helps if you don't want to eat out every meal of the day.
PM me or reply to this thread if you need a referral for the card. Honestly, its a great card with a lot of airline transfer partners.