Needing chick introduction advice

[700cct]

So to start off with, I have a hen with 2week old chicks that broke out of confinement and has been leading her chicks on a joyride around the yard. Shes not one to let me catch her or her chicks, so I let it happen. To my surprise, none of the other chickens or the rooster has bothered them, and today even, I found one of the little chicks taking a dirt nap with the rooster!
Anyway, the real question is, i have older chicks, about a month old, in a separate coop. I wondered, since the flock is doing fine with smaller chicks, if i could introduce them in now. Or would they get picked on since they're bigger and dont have a mama hen to watch out for them?
Ive never had so many chicks at one time, im hatching a lot for meat this year.

 

[Rooster G]

Mix them up is what I do as long as there is plenty of space. Sometimes I have to set an extra water bucket out because the older ones strategically block them, but eventually they mix it up especially if rooster does his job.