My condolences on your loss.

A three hour diffeence in the flight should give you enough reason for a refund without any penalty fee.

I would call AA's platunium Customer Service. I wouldn't mention the death in the family. Simply say that the three hours throws off your schedule and you believe it's your option to cancel the flight without penalty because of their change. Say as little as possible about any other details.

Also, there might be some info about the rules on that if you search around the AA website. Or once on the AA website, you could call the web help number (their phone number is on the Contact Us list) and ask them to point you to the page with the rules.

Hope this helps.