I have an update on this one - we contacted Expedia first who then put us in touch with both American Airlines and US Airways (we used separate airlines for each leg of the trip). Both airlines were very helpful and cooperative in our issue and both said they would fully refund both sets of tickets after we provided the death certificate.
US Airways actually followed through with the full refund and the credits now appear on my statement but American Airlines issued vouchers in the full amount for future flights. We’re going to pursue having the vouchers converted to credit card credits but if that doesn’t happen I’ll still be satisfied.
Some organisations still seem to know how to behave decently. That said, it often depends on how they are approached - a request is always going to be more successful than a demand.
While I sympathize with your situation, what constitutes a “special situation”. I’m sure the airlines have heard all sorts of reasons: My son came down with chicken pox the day before a family vacation. They gave him a refund (because they refused to board him), but the rest of us could either go or lose our ticket. Our next door neighbor had a heart attack 2 days before his daughter’s wedding. You guessed it: no refund.
It’s a case of “You gotta draw the line somewhere”. Just don’t expect everyone to draw the line where you do.