When can I introduce baby chicks?

[Ruby roost]

When is it good to introduce younger chicks to older chicks? This is my first year raising chickens. I got 14 chicks on May 10th so they are just over 12 weeks old, on July 2nd I got 2 more babies. I currently have them all in the same barn but the 4 week old chicks are separate from the older birds. I don’t know if age, breed or gender play a role in when you can integrate birds. Please help
12 week old birds - 2 silkie pullets, 4 silkie roos, 2 road island red pullets, 2 buff orpington pullets, 3 bantam pullets and 1 bantam roo.
4 week old birds - 1 white leghorn pullet and 1 white leghorn roo.
Here are some pics of the babies and the main coop/run. The babies are currently in the black cage in front of the coop to the right.

 

[ChickNanny13]

What is the dimensions of your coop/run? It's been recommended 4 sq ft per chicken in a coop and 10sq ft per in the run. Your's looks a good for the Silkies & bantams, however you got too many Roos.

 

[Ruby roost]

What is the dimensions of your coop/run? It's been recommended 4 sq ft per chicken in a coop and 10sq ft per in the run. Your's looks a good for the Silkies & bantams, however you got too many Roos.

The run is 12x12 and the coop is 7x12

 

[aart]

Agrees too many males.

Prop open the crate door just enough so only the chicks can get in and out.

This is how I, and others, integrate chicks:
https://www.backyardchickens.com/articles/integrating-new-birds-at-4-weeks-old.72603/