Being Yotzei others Havdala if one already heard Havdala: If one already fulfilled his obligation of Havdala he may not repeat Havdala to fulfill the obligation for other adults, [unless they are unable to say the blessings themselves]. One may however repeat the blessing of Havdala to fulfill the obligation of [male] children [that have reached the age of education and do not know to say Havdala themselves]. Therefore if one heard Havdala in Shul he may still say Havdala for his younger [male] children upon his return home.
Repeating the blessing of Besamim and Haeish: In the event that one is repeating Havdala for a person who did not yet hear Havdala and is unable to say it himself, one may only say the blessing of Besamim if he also smells the spices. It is proper not to repeat the blessing of Meorei Haeish for the listener being that he has already fulfilled his obligation. [Rather one is to have the listener say the blessing himself. If however there are children above the age of Chinuch listening to the Havdala one may repeat the blessings of Besamim and Meorei Haeish on their behalf.]
Repeating Havdala for women: A person [whether man or woman] which has already said or heard Havdala may not repeat Havdala for women that did not yet hear Havdala unless there is a man or male child which is also fulfilling his obligation with this Havdala.
One may only repeat Havdala for the sake of another person if one is saying Havdala for male children who have reached the age of Chinuch or an adult male which cannot say Havdala himself. In such an event one must smell Besamim upon saying the blessing of Borei Minei Besamim, and is to omit the blessing of Meorei Haeish having the listeners say it instead. One is not to repeat Havdala for a woman.
 See Halacha 15
 This applies even if they are not members of his family, and their obligation of education is hence not upon him. [167/23; See Kitzur Halachos Shabbos p. 114]
 Ketzos Hashulchan 96/5
 269/3; Kitzur Halachos 296 footnote 32
It does not suffice for only the listener to smell the spices as one may not say a blessing of Birchas Hanehnin for another unless he too is benefiting. [ibid]
A dispute on this matter is recorded in Admur:
The first [Stam] opinion rules it is permitted to repeat the blessing of Meorei Haeish for the listener even though he has already fulfilled his obligation. Their reasoning is because this is not similar to the blessing over spices of which we require him also to smell, as the blessing said over fire was not established for ones benefit, but rather in memory that fire was created on Motzei Shabbos. It is therefore not similar to Birchas Hanehnin.
Others however rule one may not repeat the blessing. Their reasoning is because even by Birchas Hamitzvos, only by those Mitzvos which are a complete obligation may one repeat the blessing for someone who did not yet fulfill his obligation. However those Mitzvos which are not a complete obligation, such as the blessing over fire on Motzei Shabbos, which one is not required to search for if fire is not readily available, by such Mitzvos one may not repeat the blessing for another.
Practically one is to suspect for the latter opinion in order not to enter himself into a questionable blessing in vain. [ibid]
 Kaf Hachaim 693/11
 One is not required to smell the Besamim when repeating it for children which have reached the age of Chinuch as explained in 297/7 regarding one who cannot smell.
 Ketzos Hashulchan 99/7; Kitzur Halachos 298/16 based on 178/23 and 297/7 that one say all the blessings of Birchas Hanehnin for a child in order to educate them in Mitzvos. Seemingly the same would apply here, even though it is viewed as Birchas Hamitzvos and not Birchas Hanehnin.
 See next Halacha and footnotes for the reasons.