It would be best to use the same hens in each pen until you have enough offspring to select breeders for the next generation. Mixing older hens with their offspring will only cause confusion, as you will lose track of who is who. I intend to breed roo to hen, and the following year breed son to mother and father to daughter. This will create F1 chicks... the first generation of inbreeding. Their offspring can be mated brother to sister, and their offspring can be mated to the grandparents. It's complicated, yet simple. The easy part is keeping track of which chicks came from which pen (and parents), and where they will belong in the next cycle. It gets a little more difficult when you factor in proper selection for removing or improving traits. That's the tricky part. Wrong selection can easily set you back for 1-5 years. There are many good articles on line breeding, and there are different approaches to this type of breeding. A good place to start to get a better understanding of what you're trying to accomplish is by reading "The Call of the Hen". Here's a link to the virtual book that you can flip the pages of just like a real book:
https://archive.org/details/callhenscience00hogarich