How can I best care for my two young sons while maintaining a good relationship with my mother-in-law?

I got two boy babies 4 years & 1.3 years old. My wife demised on Oct 3rd 2013 due to blood cancer. My Mother in law is widow got 2 sons both are unmarried age 22 & 24 in that one is working in Chennai, and the other one working in Bangalore, she is residing alone all day time. My mother in law age 50 years (aprx) formed a Jamaat in her house which is in Bangalore to discuss about the children’s growth and wife’s property, in presence of family members from both sides, I took full responsibility of my both the children, I don’t want to break the relationship, let the children go and come with my elder brother in law who is working in Chennai, for that she agreed. Now she is telling I will take care of my elder son as per Shariah, you take care of younger one. My parents, sister, brother are alive and healthy. Her house distance is around 7-8 hours from my place Chennai. She is mentally disturbed by the death of her husband and daughter. I request your advice as early as possible with authenticate daleel and dawah.