Mine have been out in the coop since they were two weeks old. I have two brooder lights hung in there and they use them if they're cold... but they LOVE it out there and I'm so happy I put them out there early. We have had temps ranging from about 28 to 60 and they've been fine as long as they had the option of the lamp. They use it mostly for sleeping now, and only on cold nights. They are 4.5 weeks old now. so, I say go for it if you can provide them a spot with the right temperature for their age... which I believe it 70 degrees at five week (for yours), so not too bad.
