Check step before trying to have a broody hatch...

So, I have a Buff Minorca that has gone broody in the last 3-4 days. I have made some effort to make sure she is serious. I take the eggs away every day. Push her out of the nest every day and 3 times back to back. And, she goes right back in and does not leave for treats. So, I have 28 hens and an EE rooster. I am guessing at around 2/3 fertility give or take based on what I see when I open the eggs for cooking. (Via the how to tell an egg is fertile picture topic.)

The target is 1-4 pullets, and a not broody Minorca when I am done, and a nice smooth introduction to the flock because they have a mama.

So, my plan.

1) Block off a little area around the nest the broody is using and put food and water there just for her, to keep other hens from adding or breaking eggs.

2) Pick 6 eggs from today and tomorrows lay for hatching. Do not refrigerate. Since, none of the hens are EEs and I kind of want colored eggs I am leaning towards choosing white eggs which would be from my Minorcas, Brown Leghorns, or Ancona. Not sure how colored egg genes get passed on. In any case the white egg layers are small and good layers. I figure those are good genes to pass on.

3) Put them under the Minorca. Mark 21 days on the calendar.

4) In a week or so at night sneak into the nest and candle the eggs to see if any are viable. Remove any that are not viable.

5) 21-23 days later, viable eggs should hatch. Throw out any eggs that do not hatch.

6) Switch feed to chick starter in a small feeder for the chicks and un-medicated flock raiser with oyster shell on the side for the rest of the flock.

When should I remove the separation between mama and the chicks? I am thinking as soon as possible at this point because the separation is not going to be chick proof and I don't want the chicks getting separated from mama with the rest of the flock.

Seems kind of simple when you let the hen take care of the work. What am I missing?

Cockerels will be culled.