I took mine out after a few weeks only because I get them in April and May and weather can still get too chilly for little ones.
I did however have 2 of my little ones out one time when I brought them home as it was a nice warm day, I kept them right by me and sat with them, they will go to you if they feel uncomfortable or scared and you will know if they just are not that into being out in such a big world yet.
But if the weather is nice there isn't any reason you cannot bring them out for supervised play time, after all mama chickens hatch their eggs outside.