As I'm sure you know, many times kids think they are being gentle, and are actually not. I would allow the kids to sit in an enclosed area and let the chickies wander around with NO touching or holding for at least a week. That way they can interact without any harm to the chickies. ALWAYS WASH HANDS WITH WARM WATER, as the cold hands could chill the chickies. Then make sure your kids know just how fragile they are. Chickies move and jump around a lot, and sometimes we squeeze them harder than we think to keep them from hopping out of our hands. If the kids need to hold them, have them do it while sitting down, so if the chicks jump, they don't have far to fall and the kiddos won't grab them too tightly to stop them from jumping out.
They are so tiiny and fragile, I would try to wait as long as possible to avoid the risk of an accidental catastrophe that would prove to be traumatic for the kids, and possibly deadly to the chick. Washing hands is very important for both kids and chickies, so your kids don't get salmonella or anything as well as so they don't pass anything on to the chickies unknowingly.
This is my advice. Hope its helpful.