The Tachnun Issue:
1) A shul is NOT allowed to skip tachnun when there is a bris earlier that day in the same shul (Landuas, Shomer Shabbos…) just because that minyan skipped.
2) A shul is NOT allowed to skip tachnun by shachris when there is a Chosson on the day of his Chuppah earlier than chatzos that day just because they will skip it at mincha.
These halachos are m’furash in the Mishna B’rura! I believe that Hashem needs our tachnunim, after all we can only gain instead of complain!