221:6 One would not fast for a yahrtzeit on a day on which we do not say Tachanun. One would also not fast on the day of a bris if he is the father, the sandek or the mohel. Similarly, at a pidyon haben (redemption of a firstborn), the father and the kohein would not fast, nor would a groom during the week of sheva brachos. On the other hand, one may not eat at a meal celebrating a siyum on the day he has yahrtzeit. On the days when he does not fast, the one with yahrtzeit should occupy himself with Torah study, doing mitzvos, and other good deeds in the merit of his deceased parent.
221:7 On the evening leading into the day on which one has yahrtzeit, he may not eat at a wedding feast, which has entertainment and celebration, but he may eat at the meal of a bris, a pidyon haben, or a siyum.