Did you really mean to say you plan to free-range your chickens during the night and coop them up during the day? I can think of no situation, even with adult chickens, where that would be a safe practice.
Your chicks will decide when to venture out to free range. Right now, even if you were to open the run so they could go out and explore, they likely wouldn't want to.
Chicks have a strong instinct to understand that they are prey, and especially they understand that their small size makes them twice as vulnerable. They won't be apt to show much interest in pursuing freedom for now.
I have three-week old chicks at this time, and they have full access to the entire run with sixteen adult hens. While they are fearless about mingling with the adults inside the covered run, they aren't and won't have any interest in free ranging for several more weeks.
Usually, between six and eight weeks, the chicks will notice there are open doors leading to the great world outside, and they will begin to test their courage to step out of the run. But they don't go racing off across the yard at first. They instead cling to the apron around the run, staying within its safety and cover. Chicks under the care of a broody may follow her across the yard, but not unescorted chicks. They need to gradually learn to trust themselves to know when it's safe to strike out on their own.
So, for now you may open the run up so the chicks can step outside when they feel brave enough, but do understand that it will be several weeks before they feel safe enough to actually free range. But no chickens should be free ranging all night, even if they were inclined not to want to roost and sleep when the sun sets. Not only are chickens programmed to sleep at night, they understand that things in the night are waiting for the opportunity to eat them, and they seek cover and safety at night for just this reason.
