Q. Is the case above any different than the common sheva brochos done in shul by shaleshudes during Shabbos?
Is the cup of wine drunk before havdalah?
A. Poskim disagree as to what to do when the chosson-kallah are present at a shaleshudes offered in their honor in shul. Sovea Smochos (4: 53) following Mishna Berura’s (299: 14) opinion, maintains that one can drink the wine up to 17 minutes after sunset began. Ohalei Yeshurun (5: 15) quoting Igrois Moshe opines that at New York’s latitude one can drink only up to seven minutes after the shekia.
Those who maintain that no wine should be drank after that, (Hochmas Shlomo 299, Sovea Smochos 4: 54 and many Lithuanian Poskim), would leave the two cups, (birchas hamazon and sheva brochos) until after maariv and recite havdala on the cup of benching. Then, it would be mixed with the sheva brochos cup, and it would be given to the chosson-kallah and others, as it is usually done.
However, Igrois Moshe, (O.H. 4: 69) debates at large if when reciting sheva brachos after birchas hamazon, the wine should be drank mainly by the chosson-kallah as normally done by the chupa, or by the one who leads the bentching. He maintains that that the newlyweds should drink it.
Others (Eishel Avrohom 199 and many Chassidic authorities would drink the wine before maariv and havdala.
Horav Shlomo Miller’s Shlit’a opinion is that one should follow the established minhogim of his congregation. But the common minhag is to for the chosson kallah to drink the wine.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a