I let my broodies raise the chicks with the flock from day 1. My set-up is probably different than yours. I have a lot of room. I have a pretty laidback flock. I do not have any hen that goes out of her way to go after the young chicks. I do have a rooster that helps Mama watch out for the chicks if they get separated from Mama. Not all roosters do that.
There are risks whichever way you do it, but I really like for Mama to take care of the integration issues.