We've been lucky with our family. They understand that we're a business and while we will give them a discount if they want our official services they have to pay just like other customers. Usually it's something like "We have a bunch of people coming and want to have this or that food, would you be willing to cook it for us if we buy it?"
We've done turkeys for Thanksgiving parties, steaks for family reunions, Memorial Day cookouts, etc. and everyone has contributed whether we asked them to or not.
I love my family.