Travel Voucher extension?

I have two travel vouchers that I got after a bad experience with Hawaiian ($300 each). Unfortunately, we had already done a bunch of traveling and now it’s looking like we won’t be able to use them by their expiration date (8/24). Is there a way to have these vouchers extended?

Honestly, since there are no cancellation fees, I was thinking of just booking and then cancelling, but if there’s a better way, I’d love to know.