We have five older Orpingtons and 8 Wyandotte chicks (so the newbies outnumber the oldsters!) At dusk, everyone marched into their coop. We have two ramps and two doors (one for each set of chickens during the 'division,') and I was surprised that they very quickly took to using whichever ramp they felt like at the moment. However, each returned to their old roosts, and nighttime was uneventful. Everyone is getting along together this morning in the run.
I will post pictures of the coop and schematics after I finish some aesthetic details, but the coop is 8 x 12 and the run is 24 x 12, so they have lots of room.
In the house, we have a room set aside for the chicks, and they have a large (8 x 6), plastic-lined brooder. We remind ourselves that "its only eight weeks," clean it every week, and give the room a thorough sanitizing when its over!