I'm so sorry to hear this, MC!!! I was getting ready to let everyone free range during the day while we're at work but am re-thinking that decision after hearing from you & others. Both DD & DS will be out of school soon so maybe they can let them out sooner than 4pm each day.
Hi gracejr, I just had 2 broodies, the other girls didn't bother them either. The only thing I did when the chicks came was to watch the big girls closely. My first hatch in Feb. I had a rooster who watched over the chicks as well as Momma. There was only 1 big girl that tried to bother them. The roo dealt with her each time she tried. The little ones also learned to stay away from her. I don't have my roo anymore so when one of the big girls decided to go after my new chicks I built a pen within the coop for Momma & the babies. I just didn't like the way she pecked at them. I can't answer about sneaking week olds under your girl along with the newly hatched. I'll leave that to the more experienced on this site. I got a lot of my questions answered over on the Old Fashioned Broody Hen thread. They are happy to answer and don't make you feel stupid for asking! They're good people!
In my opinion, week olds are too much of a risk - my broodies don't accept much unless they've hatched it themselves. Others have had luck. The younger the better, and sneak them in there when it first becomes night.