Prepare to be happy. Prepare to have fun. Prepare to play. Portraits should not be about looking perfect, sitting perfectly or behaving perfectly. They should be about your family being your family. They should be a record for all posterity of who you are and how you love each other. That's your job- to show up and have a great time together, just by being together. My job - to make a perfect image while you are here.
A portrait is not a snapshot - it is a composed, choreographed, timeless, individual art piece, in which the subject matter happens to be a person.