A non-Christian relative has set a wedding date for March 29, which is Good Friday. It will be in the evening so there would be no interference with Good Friday services and they are offering non-meat options at the reception ("fish" was scribbled onto the reply card, so I suspect someone approached them about the conflict after they printed up the cards). I would have no problem fasting the entire rest of the day. I'm just wondering whether the solemness of Good Friday prohibits participation or is it something that is left to prudential judgment.
Good Friday is not a holy day of obligation, and there is nothing in Church law that would forbid you from attending a wedding of a non-Christian relative held on that date. However, since your relative has been informed that there is a conflict of dates for Catholics, then it might be a positive witness to your own Christian identity to skip the reception. You could contact your relative, explain the conflict, and let this person know that you would be happy to witness the marriage but will be bowing out of partying on Good Friday.
Caveat: If you choose to do this though, please do not give your relative the impression that skipping the reception is something you “must” do, as if the Church were obliging you not to party on Good Friday. Rather, present this as something you are choosing to do as an expression of your own convictions.