How soon is too soon to be cooped?

[orrpeople]

Also, the high was in the low 70s today and they were happy as can be running and flying around in the coop for a couple hours today

They're pretty hardy - it's not really the cold (within reason) as much as it is sudden changes. It sounds like you are giving them lots of opportunities to be getting used to the temps. Like everyone has said, maybe just use a bit of heat at night.
Have a great time with your chicks!!

 

[lazy gardener]

How many chicks? What are your lowest night time temps? Do a thread search for wool hen and huddle box. I bet either of these options would allow you to move them out this week, or by the weekend for sure.