I used to breed and hand raise cockatiels.
Personaly I would not put the chicks in with the tiel, cockatiels have a tendancy to pluck/mutilate, and bite the toes off of babies that are not theirs. I would wait to place them together until the chicks are at least half grown and fully feathered.
Until then, let your cockatiel see them, have supervised "play time" that way they get used to each other without all the drama. Then when they are ready to go outside, they will be used to eachother.
Please keep in mind how slippery and fast tiels are when fully flighted. If you are planning on keeping your cockatiel outside in the coop/run "for any amount of time," you may want to add a double door into your coop, with a small walkway in between the two doors, just large enough for you to stand in and close the door behind you. That way you can go in, close the first door behind you, then open the second door into the coop/run, without your cockatiel making an escape. Also any gaps wider than an inch, I would block off, as your tiel will be able to get out. "If the tiel can get its head through, then it can get out."
I hope this helps and gives you some insite, as I would hate to hear that your tiel escaped, and is litterally flying free.
