How to get divorce from cheating husband and custody of children?

You can seek divorce from your husband on either of the grounds as mentioned in section 13 (1) (i),(ia)(ib) of the Hindu Marriage Act 1955:

1. Had the sexual intercourse with any other person
2. Cruelty
3. Desertion

During the pendancy of the petition you can move an application for interim maintenance and the Hon'ble Court will direct your husband to pay the maintenance for your self, your children and the litigation expenses, wherein after the Divorce you will be entitled to permanent alimony depending upon the financial status of the your husband and  the type of standard of living your are accustomed to.

Your husband shall also be directed to give maintenance of your two children till they attain majority even after the Divorce.

 
Moreover you can always retain the custody for the two children but  if the the court so directs on the principal and your husband contests the same also on the intention of the elder child,  you are likely to loose the custody of the elder child but if your able to prove that your husband is living in adultery your can have the custody of both the children.