If you use that pen, do not use it for long.
I do it differently. Let the big girls out to free range. Lock the new girls in the coop/run, feed along the fence. This gives everyone more space, this lets the new ones explore the set up, find the escapes, the hideouts without being chased for their lives. They begin to get used to the territory, and the old ones get used to seeing them in there.
As close to dark as you can, let the old ones in. Put the new ones in the crate if you want. Rinse and repeat for a coupe days. Then late in the afternoon, let the new ones out with the old ones. Watch carefully.
Generally there is one or two old biddies that are heartless, and the rest will follow their lead. Put that bird or pair in the crate at night. Rinse and repeat.
Usually less than a week, this will be all settled.
Note**** My coop/run has numerous shelters, hideouts, roosts and multiple feed bowls that are situated so that birds eating at one station, cannot see birds at another station.
Mrs K