Condolences on the loss of your spouse.
I wouldn't say anything to Celebrity at the moment. When you arrive at the pier, if someone asks where your spouse is (and chances are they won't), tell them that your spouse died. They probably won't ask and I doubt that the pier checkin personnel have the authority to reprice cruises. I think it's best to be honest. If at some point, Celebrity attempts to reprice your cruise higher, then it's time to make a claim with the insurance company.
Just go and enjoy the time with your family.