Currently, I've been planning 1 to 1.5 pie per person. I use 7 oz of dough, stretched to 10 inches. When I start catering, my plan will be 1.5 per person, and I'll tune it up or down based on the customer's preference, and charge accordingly.
At some parties where I know the eaters are into food and will try everything (and eat well), I plan for 2 a person.
Your typically not as obsessed will tend to eat around 1 to 1.5 per person.
Your child, or elderly adult eat's about 0.5 per person.
Sounds like business is going well! Congratulations!!!