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. We ask Allaah to exalt his mention as well as that of his family and all his companions.
If you know that your wife is resisting and you do not expect her to obey you, then you have to find a way to take the children from her to be in your country. Then if she wants to join her children she can do so, otherwise you have to divorce her and she has no right to foster them. The majority of scholars are of the view that it is a condition for a mother to be a Muslim in order to foster the children, because it is feared that she will nurture them according to her religion. Allaah says (which means): {And never will Allaah grant to the disbelievers a way over the believers.}[Quran 4:141].
There is no doubt that you, the father, are responsible for the education of your children because if you are negligent and leave them with their Christian mother in a non-Muslim country, then you will be questioned about it on the Day of Resurrection. The Prophet said: "All of you are guardians and will be questioned about those under your guardianship…, and the man is a guardian of his family and will be questioned about them." [Al-Bukhari and Muslim]
So you have to fear Allaah with regards to your children and bring them up according to Islamic principles so that they would be a credit reserved for you during your life and after you die.
As regards the order of your parents to marry a Muslim woman, Imaam Ahmad said: 'If a person is ordered by his parents to marry, I order him to get married (i.e. I rule that he is obliged to get married).'
Therefore, you have to obey your parents if they order you to get married and you are able to do so.
Allaah knows best.