I agree, get them outside now and do not even think about putting the hen out without them. I think you would cause both the hen and chicks a huge amount of stress both now and when you took the chicks out later. Nothing better than a hen raising chicks WITH the flock.
I got 7 chicks from Meyer in June and stuffed them under a broody Black Australorp at 4 days old (arrived at 3 days). I made a 18" x 5' brooding pen IN the coop but my coop is a converted 10x12 horse stall so it has more room than a lot of people can provide. Still, it could have been 18" x 24" and still worked out given the hen moved them to a nest box much smaller than that and 2' off the ground (18" access perch) at 2 weeks. The only reason for 24" would be space for food and water. Chicks have NO PROBLEM flying to 2' at 2 weeks, NONE.
The original chicken door in the coop opened into the brooding pen and I opened that in the morning after giving all the other 8 older girls their morning BOSS. I think Zorra got tired of waiting for me and that is why she moved them to the nestbox one evening. She would bring them out into the barn alley every morning and back into the brooder pen in the evening before she moved them. They were hopping up on the hanging feeder eating layer feed as often as going back into the brooder to eat chick starter by 2 weeks. Half the chick starter I bought ended up in the bin with the layer feed because they weren't eating that much of it. I don't know when they learned to use the water nipples but with Momma showing them everything they needed to know about living here both in the barn and outside, I'm sure they were introduced to the nipples or watched the older hens.
Do NOT worry about the chicks. While Zorra is the biggest hen I have, she was NOT top of the flock but she became a fearsome protector of those chicks. Even the top of the flock Anconas were running scared. If she and the chicks were between them and where they wanted to be they would wait until they could make a mad dash behind her. Nothing got within 5' of those chicks without Zorra's OK and there were only 2 girls that were allowed to mingle.