Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
First of all, we would like to congratulate you on choosing Islam as a religion and a way of life. Islam is the religion that shows people how to gain Allah’s pleasure and satisfaction, how to be happy in this world, and how to gain Paradise in the Hereafter.
Islam asks Muslims to be dutiful to their parents irrespective of the latter’s misconduct. Therefore, you should show your parents how Islam implants love and respect for parents in your heart. Be kind and generous when dealing with them. Set a good example for them in morality, kindness, generosity, politeness, and so on. By doing so, you will invite them to the straight path of Islam.
Responding to your question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states,
Foods cooked with wine are NOT lawful for Muslims. You should politely tell your mother that while you appreciate her hospitality, you cannot and will not eat such foods in the future. If your mother is a reasonable person, she would simply respect your personal choice. Your Muslim father is definitely wrong in siding with her.
Be gentle and polite yet firm with your parents on this issue. When you stand firm on your principles, sooner or later she will come to appreciate your stand. In the meantime, ask forgiveness of Allah for what you have already done. The Prophet (peace and blessings be upon him) said, “Allah has forgiven my Ummah of their unwillful mistakes.”
Another important point to remember: Pray to Allah to guide your mother and father and open their hearts to receive the truth and accept it. Surely Allah opens the hearts of those who are sincere in their pursuit of truth.
Allah Almighty knows best.
Excerpted, with slight modifications, from: www.muslims.ca