Based on the above sources, it is clear that while there is a custom to refrain from attending weddings during the period between Pesach and Shavuot, the prohibition is not absolute. Different communities have different customs regarding the observance of mourning during this time, and it is ultimately up to each individual to follow their own traditions and beliefs.
Therefore, if your friends have consulted with rabbis who have allowed them to get married on Rosh Chodesh Sivan, you may attend the wedding without violating any halachic prohibitions. It is important to respect the customs and traditions of others while also following your own beliefs and practices.
Ultimately, the decision to attend the wedding is a personal one, and you should do what feels right for you based on your own understanding of Jewish law and tradition.
May you have a meaningful and joyous experience at the wedding, and may the newlyweds be blessed with a lifetime of happiness and love.
The Rema presents a different custom regarding haircuts, allowing them until Rosh Chodesh Iyar but not from Lag Ba’Omer onwards, even though they are permitted on Lag Ba’Omer itself. Conversely, those who have haircuts from Lag Ba’Omer onwards should refrain from doing so from after Pesach until Lag Ba’Omer. It is advised that a community does not adopt both customs to avoid division and potential violation of “Lo titgodedu” (Deuteronomy 14:1).
(To be continued)