They can go outside from day one if you have the right set up. The Ca whites will need access to a warm area more than the older chicks, until they feather out.
Yep - I am looking forward to hopefully getting to go back to brooding in the coop approach the next time around (whenever that gets to be) - I am one that keeps the babies in for as short a time as possible, just do not enjoy having them in the house (enjoy the babies, just not the mess, noise, etc). I try to move my brooder babies out (meaning off the light entirely and in the coop on their own) by 5 weeks at the latest.