Let them out now. Or as soon as you can go down.
Here is my hen with her 7 babies. She is not a protective broody, so I waited until they were 3 weeks. When they could run fast enough to get out of harms way. The first few days I worried... Janet would run away if the boys came near. She would take off to the other side of the property, leaving her babies behind. They eventually figured out to follow her. Now they are six weeks old. All are doing VERY well!
If I have dual parenting going on, I let them out as soon as they are eating and drinking regularly (maybe 3 days after hatch).
That way they have two hens watching them.
It depends on the mother for the most part. I had an Orp that I would trust as a single mom on day 3. She was brutal! I also have a silkie like this.
Here is an example of dual parenting of 21 chicks. That RSL and that silkie are not the parents. Just parts of the flock. Being flogged teaches them to accept the bitties
I might just have a very chillaxed flock though. Everyone is very good with little chicks.