In that case, assuming they are mostly feathered, I think they can probably move outside soon.
I mention "mostly feathered" because some chicks grow their feathers much faster than others. Chicks that grow feathers really slowly would need to be older before they have enough feathers to move out.
You could spend a few days putting them outside in the morning and bringing them back inside at night, or you could just pick a day and put them out and be done with it.
If you look at the weather forecast, sometimes you can pick a time when their first night or two will be a bit warmer than usual, but unless there is a big temperature difference, that probably does more to make the owner feel better than to help the chicks.