I'd wait until their backs and chests are feathered in. They look like they are about 2 or 3 weeks old. Since they are still mostly covered in down, keep them in for another week or so. By then, with your weather, they should be fine to go out to the coop full time. The heat lamp would only be needed for night cooler than 65 degrees. You can start letting them outside for a few hours each day, as a sort of hardening off period. Leave them out a little longer each day. Be sure to keep them protected from cool breezes though. They definitely need more brooder space though.
Cover the brooder with a simple wire cover - this will prevent them from roosting on the side and pooping on the carpet.
That said, they can go out now (could have started out there in all honesty) as you are able to provide supplemental heat in the coop. Many people do all the brooding outside in the coop, covered run, etc.
ETA - on the heat - I am a bit of a phobic when it comes to using heat lamps in a coop, so if *I* were in your shoes and moving them outside, I'd consider the Mama Heat Pad or brooder plate over a lamp.