That's not exactly true. You can get great deals traveling to Hawaii the first 2 weeks of December. As of today you are still 10 months out. Hopefully your timeshare is finalized soon. If you put in a request with RCI for any Hawaiian island I believe you would get an exchange.
Correction: In the past, you could get great airfare to Hawaii the first 2 weeks of December. Prices have been terrible these past many months. But if they can come up with the airfare you should be able to get them an exchange. Also, are they flexible. Do they have to go on their honeymoon right after the wedding? Otherwise they can go whenever an exchange come through.