When to move to the coop

[Midwest Texan]

I have a small brood of 14 chicks. (5 Cornish, 7 barred rock, and 2 Guineas) all of which are about 6 1/2 weeks old. I would like to move them out to the coop with the older flock to free range, but I have a couple questions.
1) my older flock is on 16% protein laying feet. The checks are still on grower starter. If I move the chicks to the coop, they will all be on the same feed.
2) although they are all fully feathered, the temperatures still dip into the mid to upper 40s at night. It’s been constant mid 60s in the Bruder since I cut the heat lamp off.
What do y’all think? Thanks for all y’all‘s advice!

 

[igorsMistress]

You can feed the layers the chick feed and offer oyster shell on the side until the newbies start to lay. You can also feed an All Flock option with the OS on the side. I would move them outside now since they've been weaned from heat. If it's chilly at night they'll pile up to keep warm.