I am so sorry for your husband’s diagnosis.
Since the ticket is fully unused it can be re-assigned to another guest. The challenge is the DVC status — if anyone else in your family lives at your address or is on your DVC membership or lives in FL that will work. Otherwise they will likely need to upgrade to an Incredipass. You have 1 year from date of purchase to start using the AP voucher or it reverts to a credit towards a future AP.
Alternatively, you can try to request a refund. No guarantee they’ll do it but sometimes in special circumstances they will.