Until the young ones mature enough to force their way into the pecking order, they will probably be afraid of the adults for a good reason, the adults will usually peck them if they invade personal space. That's just the way chicken society operates. Mine usually reach that maturity point sometimes around when they start to lay. The exact timing varies a bit but usually a few days before they start to lay but more often a week or so after.
Until they reach that maturity point, the young ones learn to avoid the adults or run away if attacked. How big is your "big" coop? How much room will they have to avoid or get away? It's not a matter of square feet, it's more with the layout. My nests are pretty low to the floor so the young ones often hide under there. If the adults are on the coop floor, the juveniles are often on the roosts. I do what you are talking about doing all the time. The first few mornings I'm down there pretty early to make sure things are going OK. It always is. I'm usually comfortable after a couple of days that they will be OK. I don't know what your coop looks like and as CT said, personality of individuals can make a difference too.
How long have they been free ranging together? Saturday is still a few days away, that's probably long enough. The young ones need enough time to learn to avoid the adults. I'm not that consistent with much of anything, but I often have mine ranging together at or before 8 weeks and at 12 weeks I often move the pullets into the main coop.
As CT said, roost time is often squabbling time. The ones at the top of the pecking order get to sleep wherever they want and can be pretty brutal enforcing that right. I don't know how much roost space you have or how it is arranged, but it's really normal for mine to not start using the main roosts until they reach that maturity point where they can force their way into the pecking order. They look for safer places to sleep which just might be your nests. I integrate several times a year, this became such a problem that I put a juvenile roost higher than the nests, lower than the main roosts, and horizontally separated from the main roosts to give them a safe place to go that is not my nests. If yours start sleeping the nests this may be worth remembering.
Occasionally you get a hen that is a true brute, one that goes out of her way to attack any younger chicken. From what you describe I don't think you have one of those. I wish you luck.
