To witness to Christ: A Franciscan Friar at a wedding

What would you do?

There was a Franciscan friar who came from a family where only the parents regularly practiced their faith. The friar’s siblings had a rather checkered history with the Church, and most did not attend Sunday Mass with any frequency.
One time, he was asked to attend one of his brother’s wedding. Neither the brother nor his fiancée attended church nor did they want a church wedding. They considered that doing that would be, quite frankly, hypocritical. They did not want do get married in a house of worship simply to placate one or another family member.
The friar agreed to go but chose not to wear his Franciscan habit but a rented suit for the occasion. This was agreeable to the Franciscan community with whom he lived. The couple was planning on an outdoor wedding in a beautiful garden that had special meaning to them, and to be married by a Unitarian-Universalist minister whose spirituality was agreeable to the bride and the groom. This spirituality, as you might imagine, was not in line with Catholic teachings.
After the wedding ceremony, they asked the brother-friar if he would give a “blessing” for the meal. He was stunned and not expecting this at all, and so was not prepared.

What would you do? This is not a test to determine right or wrong. It is an exercise in real pastoral ministry and some possible responses. When you submit your answer, you'll be able to see what he did and you'll be able to see images of San Damiano, Assisi, Italy.