Well, since the invitation was addressed to the wife and son, I wouldn't go. I don't think you can get a refund on the ticket, but the rental car could be cancelled out. Have you thought about just going down and enjoying the beach or can you exchange the ticket?
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
