22:5 When praying in a Shiva house, or in the home of the deceased even if none of the mourners are there, Tachanun is not said. This is the case the entire week of Shiva, even on the afternoon of the last day. One does not even say Tachanun after returning home after a Shiva minyan. If a mourner is in shul (or in someone else’s home – MB 131:20), the congregants still say Tachanun, though the mourner does not.
22:6 Tachanun is not said in a shul where a bris is about to be held, or if the father of the baby, the mohel or the sandek is present, even if the bris is to be held elsewhere. If mincha is held at the baby’s home before or during the festive meal, Tachanun is not said. After bentching, however, Tachanun would be said. Nevertheless, the baby’s father, the mohel and the sandek do not say Tachanun that entire day, which is like a festival to them. (If davening is held is someplace other than the baby’s home, Tachanun would be said even before the meal – Mishnah Brurah 131:25.)