Here's how I solved my problem
Fortunately, I have a chicken wire box of sorts that has a chicken wire top. It's a box given to me by a friend & created for her by her dad to keep her cat in. It's probably 4' by 4' - so not small. I just put that inside the run for the 2 little birds to be in the run but not where the big girls can get to them. Then at night, they are biting the bullet to get out of that so they can roost up high somewhere - and I think they know they are not safe out in the open like that (the run is not coon safe).
To solve that problem and to get them out of the run which is not coon proof -- I took a tall bird cage I had laying around and set that in the coop. On top of that I put the small collapsible dog kennel that you can get anywhere. I ran a wood 1x2 through the bars for a roost. This put the 2 new birds at the same roosting height as the older birds but protected. So in the evening I go out and carry the young ones into the coop and place them inside this dog kennel. The older birds see these new birds at their level each night and morning. I don't know if that will make any difference when I go to release them together or not. I am hoping it influences the pecking order in some positive way. The kennel is really too small - they just have room to move around a bit and there is water & food in it if they need that before I get out in the AM to move them back to the kennel. But since it's only 2 birds.... it works for now.
So my plan for future chick additions is to do this --- I have one of those dog play pens --- they are open at the top and collapsible sides and generally have 5 or more sections depending on how large a play pen you buy. Mine is a large one but my goldendoodle sleeps in it at night as a kennel. I plan to put that thing inside the coop - since it can be contorted into various shapes, and the sides can be folded in until I need additional room for growing birds. My future little ones will be in that. Until they have some teenage size on them. Then I might just reverse that and put the older birds in the pen and let the teenagers have free roaming privileges. That might reverse the pecking order.... or so I am thinking.... or at least knock the older birds down a few notches. We'll see.
I'm going to take some pictures of my new coop and this arrangement later this afternoon. Look for some photos later.