prophet said "empty stomach would drag you to to kufar"
Don't under estimate economics. Kids would be scared to think out of their fathers sphere.
Only I think If they become economically independent can make choice not to eat haram any more.
I asked this specific question form a learned scholar and his reply was that kids are dependent on father for and he is their provider. They do not share the blame if he is using haram means of income. When they become independent they can go on their own marry way. If they know that their father is earning haram key kama-e and they are wise enough to understand this then they should request their father to use halal means of earning lively hood and stop using haram means.