Shingles can occur with any child at any age, but is more common after ten years of age. It is spread by direct contact with the rash, which differs from the respiratory spread of chickenpox. This rash tends to crust over and dry up over a week's time, if not sooner, just like chickenpox. Complications are rare, although sometimes the rash can become superinfected with bacteria germs. We do get a bit more concerned when it is on the face, particularly about the eye.
As long as all the kids in the nursery have normal immune systems that can fight exposure to infections well, I would not be overly alarmed. Zoster is contagious only to those people who have not had chickenpox or the chickenpox vaccine. The course of this disease is usually mild and the prognosis good. However, if some children in the nursery cannot fight infection normally, I would have them call their doctors immediately to tell them about the exposure.