Ok I understand. If there are 6 people in the home, depending on the size of the duck since all breeds are different and not all butchered birds weigh the same, it could take up to 2 ducks to feed all 6 people, depending on their appetite for duck as well as the duck's weight and meat ratio.
I would research this more and kind of get an idea on what your family's needs would be based on the breed you have chosen to process. Like
@humblehillsfarm mentioned, if you haven't had duck before you may want to try out a duck from the store or from someone local with all of your family to give you an idea on how many ducks you'd be consuming per week. I understand you say they would eat whatever was made, but if someone doesn't like duck much, or if you realize that your family can eat 2 ducks for dinner versus just 1, that would have to be accounted for also.
That being said, there is much to research and consider when it comes to raising meat birds of any kind. I would start small at first and kind of go from there.
If I may ask, what breed did you end up choosing?