Torn

My employer is asking people to volunteer for an assignment working with FEMA for the hurricane Katrina victims. It's a 12 hour day, 7 days a week job for a minimum 30 days doing whatever FEMA needs. I feel like I really need to help out. I also worry about how my family would cope in my absence. I know the 30 days is unrealistic and I would most likely be gone for 4 - 6 months. Is it fair to ask my parents to take over my duties? Is it fair to my kids to be without their mother for months on end? I am torn between my sense of duty to my family and my country.