149:2 If a bachelor married a virgin (i.e., a woman who was never before married) or a widow, or if a widower married a virgin, they still recite sheva brachos at the wedding meal, even if they didn’t eat during the day of the wedding, just in the night that’s after the wedding day – or even the next day! This is because the first meal is like new faces. However, after the first meal, for the seven days of rejoicing, sheva brachos are only recited if new faces attend.
149:3 When there are no new faces, if the people dining with the couple aren’t members of the family but are friends there to make them happy, they don’t say “d’vai haseir” (“banish grief”) but they do say “nodeh l’shimcha” (“we give thanks to Your Name”) and “shehasimcha b’m’ono” (“joy is in His abode”). After bentching, a second cup is taken and the bracha of “asher bara sason v’simcha” (that G-d has created joy and gladness) is recited. Then, they take the cup used for bentching and recite “Borei pre hagafen” over it. A minyan of ten is not needed for this; it is recited even with three, though not when dining only with family members.