A Christian woman got married in a church then
    became Muslim
Question

                Assalamu Alaikum:
    Upon chatting with a Muslim sister who recently moved to our community, I
      came upon something disturbing. She has been married for about 7 years (she was Catholic
      at the time and al hamdullilah she has reverted to the right path). Her husband was a
      brand new Muslim at that time. They were married in a church by a priest. He did not know
      any Muslims at the time and thought that marrying the people of the book could be done in
      a church. It was only last week that they both found out that the ceremony should have
      been conducted by a Muslim. They already have 4 kids. What are they supposed to do now? Is
      their marriage contract valid? Do they have to redo the ceremony? What about all the years
      they have been together not knowing that Muslims do not get married by priests? 
    Please advise, so that we could correct the situation if it needs
      correction.
    Jazakum Allah Khairan.
Praise be to Allah.Who has guided them to Islam. We ask Allaah to help us
    and them to be steadfast in adhering to His religion. In response to your question, if the
    marriage was contracted through an offer or proposal (eejaab) from the walee
    (guardian) of the bride and acceptance (qabool) on the part of the groom, with the
    consent of the bride, in front of two Muslim witnesses of good character (as regards
    piety, attitude, conduct, etc.), then the marriage contract is valid. Ibn Qudaamah (may
    Allaah have mercy on him) said: “A marriage is not properly contracted unless there
    are two Muslim witnesses, regardless of whether the bride and groom are both Muslims or
    only the groom is. This is what Ahmad stated, and it is also the opinion of
    al-Shaafi’i.” (Al-Mughni, 9/349; al-Mufaddal fi Ahkaam
    al-Mar’ah, 6/120).
    If the marriage was conducted as described above, then it is valid,
    otherwise it must be repeated. It is permissible for a non-Muslim woman to be married by
    her non-Muslim guardian, but if she becomes Muslim, this role can only be played by a
    Muslim. If she has no Muslim walee, then this role can be delegated to the director of the
    Islamic Centre or whoever is acting in his stead. As regards the children who were born
    during this time, they are the children of the man and should be given his name, as is the
    ruling in cases where there is uncertainty of this nature.
And Allaah knows best.