ANSWER:

It’s not permissible at all to have mixed gatherings 

You must make an arrangement to take the phones from all females at the ladies entrance and give them tokens so that they would recollect their phones while going back.

QUESTION: I m going to marry إن شاءالله, but in walimah generally girl and boys are present and people come and see them,in separate place but I fear that some women might take pics of my future wife despite warning, can I give walimah by breaking custom that boy and girl should be present on walimah day?Advise me plzz