80 new chicks and 25 new ducklings -- How to introduce to 75 hens?

[Shanti Permaculture Farm]

Hi I have 80 chicks about two weeks old and 25 ducklings one week old. Currently they are set up in my greenhouse with a light, food, water, etc. After some time, I would like to bring them all to my main chicken coop. I think I am supposed to wait six weeks. Please confirm.
Once I introduce them, I'll put the chicks into the coop during the day when the hens are out free-ranging. I think I'll need extra roosting space. I want to do this with the least damage and fear to the chicks.
Can you confirm the amount of time I should wait? Also the process of introduction?

 

[crazy4ChickensNducks]

I wait at least 12 weeks, but the bigger they are the better. At 6 weeks they can easily be killed.