Mixing new chicks and old chicks?

[Saraschickens]

Hi! I have 21 chicks right now. They are 3-4 weeks old. I decided to get some new chicks to add in with them today. 7 Black Copper Marans.
I'd introduced my chicks to outside dirt multiple times now, and they've started going outside too. Today is their 3rd day outside, and I'm working on a bigger outdoor cage for them this week. I have them in the indoor brooder in the nights. There is a brooder plate in the brooder and one in the outside cage (Tractor Supply chicken cage).
My question is, I was going to bring the chicks home and put them into the indoor brooder, and let the chicks meet in the last hours before bed when the light goes out.
And then take everyone out to the outdoor pen in the morning.
Is that too much exposure for the new chicks?
They've never been outside or introduced to dirt yet. Is it ok for them to eat the other chicks poops and outdoor dirt this quickly? Thank you!

 

[Saraschickens]

Oh ya, the new chicks are 2 & 1/2 weeks old. My oldest chicks turn 4 weeks tomorrow, but they are bantam D'uccles so they are still super small in comparison. And my 3 week old chicks are DSL Barnevelders and Polish.

 

[rosemarythyme]

I don't see why it'd be an issue if they're in the same dirt and such the other chicks are. Have Corid on hand if you're concerned about the possibility of coccidiosis overload.

I'd think about doing the introduction earlier in the day though, outside (assuming there's more room outside) and with supervision at the start. Space and a less familiar setting should help with any bullying issues that might pop up.

 

[Saraschickens]

I don't see why it'd be an issue if they're in the same dirt and such the other chicks are. Have Corid on hand if you're concerned about the possibility of coccidiosis overload.

I'd think about doing the introduction earlier in the day though, outside (assuming there's more room outside) and with supervision at the start. Space and a less familiar setting should help with any bullying issues that might pop up.

Thank you!
I picked them up at 3pm. I had my others in the outside pen. I put the new 6 in the others' night time brooder for the day. Around 7pm I brought the others in and put them in the brooder with them together, watching like a hawk. They huddled under the brooder plate.
After a while, when the bigs simmered down I put them towards the food and water, and they seemed to mingle in nicely. After about 10-15 minutes every one was eating, drinking, falling asleep together, and totally seem integrated! I love it! It went really nicely!

I have Corid on hand. I've never used it before, and hoping I'll never have too!
Thank you for replying!

I think tomorrow, I'm going to put the olders out and keep the news in so I can evaluate them, get to know them, and give them another day to aclimate.
One had a little poo butt, so I want to make sure that stays good, and also make sure they're eating and drinking.
Plus I want to give them some Save-a-Chick (electrolyte, vitamin, mineral) water.

I'm always open to any other good advice! Thank you!