1. you should file for maintenance for your two children.
2. Your marriage is illegal if he has not taken divorce from his first wife ,before marrying you.So since the marriage is void you do not have aright as wife.
3. Since the marriage took place in front of his wife and family there is no defense you can take that you were not aware about his marital status and as you are aware, the mere hindu vedic ceremony of marriage will not make it legal as the first marriage was still existing.
You should file for maintenance of your children as early as possible they can get maintenance till they are 18.
File a petition for maintenance and an injunction suit demanding not to alienate his pension benefits and other source of income till the final order of your maintenance as there is a chance that by that time court give and order finally in the maintenance petition he will transfer or give all his money to others. Find out if nay property is existing in his name.
Your husband can be charged and tried for Bigamy under IPC if his first wife complaints.but you cannot complain as you are also a party to it and was aware about his first marriage. However 419, 420, 493 of ipc can be charged against him. You can also file for domestic violence case against him under the protection of women from domestic violence act, this has to be done carefully asking only the related sections as he will defend that you are not legally wedded so no domestic violence can be maintainable.
consult a good lawyer and proceed as early as possible before he alienate his pension and other benefits
your children have the right in the ancestral property, if there is property , you as a guardian can take legal steps for partition.(consult your lawyer regarding this with details)
Now you should not keep quiet, it involves the future of your daughters.he is liable to pay for their education.
His self earned property can be asked if he dies and property is still in his name.while he is alive his own earned property can be dispersed as he likes but not thee ancestral ones.