We've always left our chicks out in the coop since they were about a month old/4 weeks, but it's pretty warm here. It's 25 degrees at night in the summer.
Maybe if they like being outside you could put up a lamp up in the coop so if it gets cold at night they can warm up.
Glad you joined us! The daytime temperatures are good, but I'd still keep them indoors at night for another 2 weeks before letting them sleep outside without supplemented heat.