Please could you explain exactly what happens in the process of Nikaah - should we perform it in a Masjid or is it acceptable to take place in a house or hall for example? Also, please clarify if it is permissible to perform the Nikaah in front of the presence of both men and women?
And finally, when agreeing the marriage contract, agreement of the Maher is made. I have been told that an agreement of a divorce payment should be made, which the husband would have to pay to the wife if the marriage ends in divorce - is the correct or not?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

It is not an obligation to conduct the marriage contract in the mosque, but the majority of the scholars said that it is desirable to conduct it in the mosque as it is an act of worship. The Prophet said: "Announce the marriage contract, and hold it in mosques and beat the Duff (percussion instrument consisting of a single drumhead of skin stretched on a circular wooden frame) in order to proclaim it." [At-Tirmithi] However, some scholars classified this Hadeeth as Dha'eef [weak].

It is permissible for women to attend the marriage contract with men, as long as they are separated and there is no forbidden mixing or cause of temptation, and provided that women fully adhere to Hijab.

In case these conditions are not met, it becomes forbidden for them to attend.

Besides, it is not a condition for the validity of marriage to mention the amount of dowry whether it is paid immediately or delayed to an appointed time. Allaah Says (what means): {There is no sin on you, if you divorce women while yet you have not touched (had sexual relationship with) them, nor appointed unto them their dowry.}[Quran 2:236]

This is called a negotiated marriage as the dowry is not mentioned.

However, it is desirable to mention the dowry as this is the guidance of the Prophet with his wives and his daughters, and this prevents any difference or disputes that might arise on the amount of dowry.

If the dowry is made known to the bride, then it should be made public whether it is paid immediately or delayed to an appointed time, in order to avoid the dowry being indefinite, as this causes disputes. Moreover, it is not an obligation to assign a delayed dowry in a marriage contract [to be paid to the wife if the marriage ends in divorce]; however, if it was made a condition on the husband to pay a delayed dowry and he accepted it, then he has to fulfil it, as the Prophet said: "The Muslims should fulfil their conditions in what is permissible." [At-Tabaraani]

Allaah Knows best.