is it permissible for a chassan and his immediate family to take haircuts on 32 baomer?
For the choson it would be allowed, similar to taking a haircut erev shabbos before the aufruf, because the simcha for him starts from the shabbos before. Regarding the rest of the family, they should not take a haircut during sefira according to most poskim, R’ Moshe zt”l held that in the rare event that their hair has grown so long that they wouldn’t come to the chasuna otherwise, then they would be permitted to take a haircut. Practically though, it is hard to see that that would be the real situation.
When Lag B’omer is on Sunday, for the Ashkenazim it is permitted to take a haircut on Friday, (however the chasuna will not be on motzei shabbos for practical reasons.)
Dagul M’rivava 493-2, Sharei Teshuva ibid 7, Shut Rabi Tiya Vayil- 40, Igros Moshe O:CH 2-95, It should be noted that R’ Moshe does not differentiate between the chosson’s family and other guest. Rema O:CH 493-2.