Food cooked with alcohol may not be deleterious to the body, but perceptions of having alcohol around the house may be deleterious to the soul.
The purpose of pain is to warn of sickness and danger; and to develop feelings of empathy for others who may suffer pain.
We cannot control our relatives lives and must respect their choices, even if we disapprove. God will reward us for patient service and enduring.
Mormonism teaches that suffering has a purpose. We must do our best to love and serve those who are at this point in their lives.