From what I understand, chicks should be left alone for the first 24 hours of receiving (or hatching, of course). Their change of place is stress enough for the first day.
After that, it is all right to handle them (picking up from underneath, chicks are very afraid of things coming from above them) one or two times a day. And only for a few minutes at first.
Once they are a bit bigger, a week or so, you should be able to handle them quite a bit, tho, again, careful not to stress them.
After that, I pretty much play with them whenever I want to. Mostly, I like to snuggle them in the space under my chins and speak softly to them.
Now my chooks are almost 6 weeks old, they think I am one of them, and they hardly pay me any attention at all, I am such a normal part of their life out in the new coop. Well, unless I bring treats, lol!
Enjoy the babies!
Bright Blessings