I have decided that either tomorrow or Friday is the Big Day. The main coop will have a screened divider put up between the 8' side and the 12' side, then Rex and his young women will be moved into the 12' side to get used to that room, roosts, feeder, etc., for a day and one night without hassle from the current residents, who will be relegated to the 8x8 side.
Shadow, the banty Cochin, and elderly Reba and Sunny will be moved into the bantam coop with the 7 D'Anvers and the Phoenix pullet (should be some interesting fireworks there). The two Brahmas will stay in that coop and I'll add to them Isaac with Tiny, June and Emily as planned, so Ike will have 5 hens in a coop he's already lived in twice in his life.
Nugget and her 9 week old son, Ranger, who hasn't been rehomed just yet, will move into the main coop. Tomorrow, the barrier will come down and the newbies to that coop will meet the older residents and get acquainted with the new much larger pen and have the pleasure of being hounded and chased all over.
ETA: It's done. Everyone is where they were going, except I decided for the time being to put Nugget in the bantam coop with her 9 week old son-when he is rehomed, she may end up back in the main flock, just depends. Have to go check to see where everyone ended up roosting for the night.