Reference: I’laam al-Mu’aasireen bi-Fataawa Ibn ‘Uthaymeen – Page 382
Question: What is the ruling regarding the gathering together of men and women in the same place? And likewise what is the ruling regarding their gathering together to eat?
Response: As for the gathering together of the family[1] in the same place – with men on one side and women on the other, then there is no harm in that so long as there is no fitnah we are aware of [which may emanate] from some of the men or women, in which case the gathering should not occur. Other than that, the basic principle is one of permissibility.
As for [men and women] gathering together to eat, then this is not correct. [In such a situation] it may be that a woman sits next to a man who is not her mahram, nor her husband. Also, how will she eat if she is maintaining her hijaab (niqaab) over her face – which is necessary to be uncovered – since it is obvious the food is [to be] put in the mouth, [something] which necessitates the uncovering of the face?!; Because of this [reason], we are of the opinion that such a gathering should be prevented.
As for the presence [of men and women] in the same place and gathering – or in an auditorium, then there is no harm in that, so long as the men are separated from the women.
Footnote:
[1] It is clear from the rest of the Shaykh’s response that he means the immediate family, in front of whom the women are not required to cover their faces – namely their husbands and mahrams, wAllaahu A’lam.