Bar Mitzvah in a Hotel on Shabbat with Extended Family during the Year of Mourning

A mourner within the year of his mother's passing, whose brother is hosting a Shabbat Sheva Brachot for his son in a hotel for the entire extended family. The family always gathers for all celebrations, and if one of the uncles is absent, it will be noticeable that he did not come due to mourning. Can he attend the Shabbat to avoid public mourning?

The mourner can attend the Shabbat with the family. It is preferable for the wife to enter the hall first, so if the husband does not enter, it will be more noticeable as public mourning.

There is a disagreement among the later authorities about whether there is a prohibition of public mourning during the thirty days and twelve months of mourning. According to the opinion of the Shach in Siman 393, Subparagraph 7, and also in Siman 400, Subparagraph 2, and as written by the Beur HaGra there, Subparagraph 3, and Chayei Adam in Kast 9, and other later authorities hold that mourning for thirty days and twelve months is observed even publicly. However, in the Gilyon Maharsha, Siman 393, Paragraph 4, and as written by the Yaavetz in Shut, Part 2, Siman 180, and also in Shut Pnei Yehoshua, brought in the Graaz Margaliot, Letter 26, and in Pitchei Teshuva, Siman 391, in the name of Adnei Paz, and other later authorities hold that public mourning for thirty days and twelve months should not be observed, and this is the custom, but there are those who are stringent.