Is serving food to my father, who gambles with his friends in our house, considered unlawful or lawful?

There is no obedience to a creature in disobedience to the Creator. Therefore, it is not permissible for the questioner to assist her father in gambling, such as preparing the gambling tools, because it is a grave sin. However, preparing food for them is not included in this, as it has no relation to gambling. It is recommended to supplicate for the father's guidance and for the daughter to strive in advising him through appropriate means. If he does not respond, she has fulfilled her duty.