She drinks wine in front of him and he is afraid that if he divorces her, she will take the children, and she is a kaafir

Although marriage to a kitaabi woman – a Jewish or Christian
woman – is permissible, there is a great deal of risk involved in that, the
most serious of which is the danger to the religious commitment of the
children and offspring, because she may try to corrupt their religious
commitment, especially if she lives in a non-Muslim country. 

How can you convince your children that drinking alcohol is
haraam, when they see their mother drinking it? 

Many scholars are of the view that if a Muslim man marries a
kitaabi woman, he may stop her drinking wine and eating pork. This is the
view of the majority of Shaafa’i and Hanbali fuqaha’ and it is the view of a
number of Hanafis. 

It says in al-Bahr al-Raa’iq (3/111), quoting from
some of the Hanafis: The Muslim may forbid his dhimmi wife from drinking
wine, as he may prevent his Muslim wife from eating garlic and onions if he
dislikes that. This is the truth as is obvious. End quote. 

It says in Mughni al-Muhtaaj (4/314): The kitaabi
woman who is married is like a Muslim woman with regard to spending,
division of time (in the case of plural marriage) and divorce. She should be
made to do ghusl after menses, nifaas and janaabah, and she should not eat
pork according to the more correct (scholarly) opinion. Both she and a
Muslim wife should be forced to wash off any impurity that gets onto their
bodies. End quote. 

It says in al-Insaaf – a Hanbali book – (8/352): The
dhimmi wife should be prevented from drinking any intoxicant to the point of
intoxication, but he does not have the right to forbid her to drink amounts
that do not intoxicate, according to the correct view. This was stated by
Imam Ahmad. And it was narrated from him that she should not be allowed to
drink it at all. It says in al-Targheeb: the same applies to her
eating pork. End quote. 

The Maalikis are of the view that he does not have the right
to stop her drinking wine or eating pork, as it says in al-Taaj
wa’l-Ikleel (5/134). 

If you are not able to stop her, because of what you said
about the fact that she may ask for a divorce and take the children, then
you must explain to your wife that it is part of kindness and good treatment
among spouses not to drink wine openly in front of you. If she insists, then
you should keep away from their gatherings, as a sign of denouncing evil, as
Allaah says (interpretation of the meaning): 

“And it has already been revealed to you in the Book (this
Qur’aan) that when you hear the Verses of Allaah being denied and mocked at,
then sit not with them, until they engage in a talk other than that; (but if
you stayed with them) certainly in that case you would be like them. Surely,
Allaah will collect the hypocrites and disbelievers all together in Hell”

[al-Nisa’ 4:140]

This general principle applies to everyone who is unable to
take action against an evil; he must leave the place where the evil is being
committed if he is able to, otherwise he will be a partner in the sin. 

You have to be patient and do everything you can to call your
wife to Islam; make her love Islam by your attitude and actions. We advise
you to make du’aa’ for it is the greatest of weapons. May Allaah guide her
and her family at your hands. 

And Allaah knows best.