It won't hurt anything to put the nesting material and fake eggs in. It does give you a better chance of trying it out to see if there are problems while you have time to fix the problem. A couple of examples.
Some will probably go in the nest, exploring and scratching, looking for something to eat. Or maybe they just like to play. If you find the nesting material and fake eggs on the floor of the coop, that means you need a higher lip on the nesting box to hold that stuff in. Once they start laying, they will scratch and rearrange the nesting material to make a nice cozy nest. If the lip is not sufficient, a previously laid egg could wind up on the floor.
Sometimes some of them do want to sleep in the nesting boxes. The nesting boxes don't have to be higher than the roosts for that to happen. Sometimes, when they are transitioning from sleeping on the floor to sleeping on the roosts, they spend a night or two in the nests. Some can get in the habit of sleeping there instead of continuing to the roosts. I have had the problem that the ones lowest in the pecking order get beat up so much by others on the roosts that they look for a safer place to roost. The nesting boxes can look like a pretty safe haven. This is after they have been on the roosts for a while. I've especially noticed this with broody raised chicks that are fully integrated with the flock and are used to roosting on the roosts with Mama to protect them. But after they are weaned, they may get picked on and find a safer place to roost. It has also happened with brooder raised chicks, but these are the ones that get stuck in the nesting boxes and never make it to the roosts because of the older bullies. It does not happen every time, but it has happened.
So my suggestion is to go ahead and prepare them. You probably won't have issues, but in case you do, you have a chance to fix them.
