We have 3 12 week old chickens. They haven't started laying. My FIL has a connection to get 2 new chicks. Can we let them be in the same coop with our other 3 or would they need to stay separate until older? Also, we live in AL & the lowest it gets @ night is 68. Would the new chicks need to be inside at night or would a heat lamp out in the coop be ok?