Again, thanks for all the input....
I ran into the player last night and talked to him personally. As a Junior in high school, I felt it would be good to talk to him directly to find out what he knows about the situation.
He indicated that his mom hadn't told him anything about the re-scheduled date for the family get together. In his words, "Probably because she knows I'm going to fight her about it".
I told him about the policy of sitting double the number of games missed, and he said of course that he knew about it and would discuss things with his parents. I let him know that I would not have a problem if he could make it for the Friday game and the first game of the DH on Saturday as we generally try to get everyone in on DH's, and he would probably sit one game anyway.
I guess that was my compromise: be there for 2 games and you can leave early on Saturday for your family reunion, without loss of playing time. I even offered the suggestion of driving him 1/2 way to the family reunion later Saturday if he wanted to stay for both games.
We'll see what happens.