I've watched our Java Mommas lead their little ones out into the yard at just 3 days old. With multiple chicks however, usually, one just cannot figure out the concept between inside and outside (or that there is a door), gets stuck in the coop and yells for all it's might while Mom runs up and down the ramp (again and again). It's funny to watch. However, the problem becomes getting everyone inside at night. That's where you need to help out, otherwise chicks get stuck outside at night - so at dusk, I go out into the run and watch Mom lead everyone inside. Usually, by the third night the chicks have learned how to navigate the ramp and all tuck in by themselves. (So I introduce the concept of 'ramp' starting Friday morning, and by Monday night they've got it)
However, you've got to look carefully at your fencing, the gaps below the gates, etc. You'd be surprised where a little chick can get through and into and oy vey! I can't tell you how many times we've had to rescue a chick from a tight spot. Thankfully, the chicks typically yell their heads off!
As for the other hens - yes, you need to create safe spaces for the chicks to be outdoors to play for the first few days. Whether that's a seperate fenced off area; letting your other hens free-range while the chicks are in the yard with Mom's; just be aware that the other hens may take the opportunity to be defensive. That's not pretty. And those girls end up on the dinner table the following night! I do not tolerate a hen who attacks chicks (her own or anyone else's). Hard to do if you've paid good $$ for these things - but in the long run, very much worth it in terms of your overall flock goals.
It's getting fun, isn't it?!
