During the day they have access to the coop, run (unless the babies are in there), and fenced yard.
At night they are in the coop.
coop 8' x 16'
run 8' x 12'
yard 30' x 50' (will double in size next summer)
Flock = 21 (not including the three babies), more or less in pecking order:
1 Dark Cornish mix
4 Silkies
1 Orpington
1 ISA Brown
1 Wyandotte
3 Easter Eggers
4 Sussexes
1 insane Polish (she's insane and I'm insane for getting her)
1 Jersey Giant (not giant)
2 Welsummers
2 Belgian bantams
As you can guess, I went completely nuts at the feed store last spring. Not exactly a utility flock, but they're really fun to watch. And yes, I would do things differently in hindsight: fewer birds, fewer non-utilitarian breeds.
Also I'm not planning on enlarging the flock.
You have gotten many helpful answers from those with far more experience than me, but I just can't help adding my perspective. It sounds to me as if you have plenty of room, really, and that you only need to do a couple of things differently.
I would first say that until the extreme minority of three have grown larger, I would not be in a hurry. They have to have enough size and confidence to adequately defend themselves if they are cornered.
Second, I would add the littles to the coop at night while the older girls are already roosting and settled (and night blind), and do so either by placing them on empty spots on a roost where the three are together, or by placing them inside a crate with a roost and an open doorway on the floor of the coop, so in the morning when they all pile out the pop door they are all together coming from the same home base.
Third, until the three have gotten some size, I would follow the advice of another poster who suggested confining the older girls to the run and giving the youngsters the yard to learn, and in keeping with the earlier suggestion, put them in hiding places and let them go into and out of them several times, put their food and water in them even, so they consider them a safe place to eat and drink, but ensure they cannot be tipped over, and the entrance/exit is too small for any of your older girls, with the possible exception of the Bantams obviously - and if there is any danger the Bantams will bully them, have two openings, so if they are chased into one they can escape.
This last (switching access to run versus larger enclosure) I would kind of alternate on, so it gives the smaller ones time to learn the larger enclosure, and kind of keeps the older ones off balance so they maybe aren't quite as sure of themselves. It might take some temporary wire walls so the older ones still have access to nest boxes and the like. As the youngsters gain size, start putting the older birds with them in the larger enclosure one or two at a time, from the bottom of the pecking order up.
Obviously if you are free ranging you have more room for sharing, but in your situation, I understand why you prefer not to free range for now. Neighbor dogs are the greatest danger - they are usually not afraid of you, like a coyote or fox might be.
I worked with some of them last night and was amazed at the weight they had put on since I had lifted them last week. Comin' along like a house afire! 
).
