When should I add babies to our flock?

[FunWithFowl]

Hello all, hoping someone will have a suggestion for when I should add our babies to our older flock. Here are the details..... We got our older girls on May 10, 2012; so they are about 2 1/2 months old. We have 4 hens and 4 ducks in that group. Our next group which I refer to as our babies are 1 and 2 weeks old. I currently have them in a brooding box in the coop. I am wondering at what age can I introduce the babies to the rest of our girls?
Thanks!

 

[Kevin565]

What breed is everyone?

 

[FunWithFowl]

What breed is everyone? 

Older girls: 1 Araucana, 2 silver laced Wyandottes, 1 leghorn & 4 Pekin ducks. Babies: 1 buff, 1 golden campine, 1 partridge rock, 1 Delaware and one Easter eager.

 

[growyourbrew]

They have to be almost as large as the older ones. A good way to introduce them would be to let them in see each other but in separate areas