Age gaps in chicks?

[Harmoni]

We currently have 2 flocks separated by chicken wire. The original flock are all adult hens. The second flock is a mixture of little cockerels (unintentionally) and little pullets. They range in age from about 8 weeks to 12 weeks.
I am planning on picking up 3 4 week legbar chicks tomorrow. Do I need to keep the 4 weekers separate or can I put them in with the 8-12 weekers? I have a potential spot I can keep them in a larger dog crate in my coop, but not other run space keeping them divided outside. I would think keeping them in a dog crate 24/7 wouldn't be an ideal scenario. I have a popup day time run I could put them in, inside the run that the 8-12 week chicks have.
Any advice would be appreciated!

 

[JacinLarkwell]

I wouldnt mix them

 

[Harmoni]

I wouldnt mix them

Because of quarantining or because the age gap is too big?

 

[JacinLarkwell]

Because of quarantining or because the age gap is too big?

Both

 

[JacinLarkwell]

4 weeks are like elementary school, 12 weeks is like freshman year in highschool

 

[Harmoni]

4 weeks are like elementary school, 12 weeks is like freshman year in highschool

The youngest 2 are only approximately 8 weeks though. The oldest is actually the least aggressive to her flockmates. I only know the actual age of the 2 I hatched which are both cockerels. They will be 8 weeks on monday. I have 3 that are likely a few days younger than them, I got them at rural king on a sunday, was told they get delivered on Friday, so hatch date of approximately that Wednesday, so they will be 8 weeks next Wednesday.
Then I have 3 that are around 9-10 weeks and 2 that are 11-12, I can't be positive as I didn't hatch them.
Here's a recent pic of the group.

 

[Harmoni]

Edit, 2 that are younger than the ones I hatched. We had 3, but one died and we replaced with a slightly older one.

 

[JacinLarkwell]

I still wouldnt nased in biosecurity

 

[Harmoni]

I still wouldnt nased in biosecurity

I don't have the room for a true bio security quarantine. You need to keep the new birds 30+ feet away. I don't have a yard big enough for that. I would have to put the new 3 in my brooder in the house and make sure my kids didn't go near them before going outside to the other chickens.

 

[aart]

I am planning on picking up 3 4 week legbar chicks tomorrow. Do I need to keep the 4 weekers separate or can I put them in with the 8-12 weekers?

8-12 weeks is plenty old to be territorial.
It might work out just fine...but best to have a separate but adjacent enclosure for the new ones.

I don't have the room for a true bio security quarantine. You need to keep the new birds 30+ feet away.

It's more like 100-300 feet, downwind,but if you can't do it, you can't do it....
.... and will have to assume the risk.

Biological/medical quarantine:
BYC Medical Quarantine Article