Perhaps......A scavenger hunt to find items in the pyxis or to located specific items in a crash cart.
Your charge nurse idea is a good one.
Have one or two be responsible for passing meds -or- maybe find and empty room where they can practice putting the beds in all the different positions.
How about having them locate specific information in a patient's chart (labs,secondary diagnosis, errors -such as improper abbreviations.
Do you think any of them will be looking for a job at your facility when they graduate...If so...maybe give a complete tour of where other departments are located in the hospital (places they will need to know how to get to...blood bank, pharmacy, MRI, CT, etc.)
Because it is a peds unit, how about having them bring a book to read to the patients while mom or dad take a little break.
How about giving them rhythm strips to identify -or- find out what thier next test in on and give them one or two questions each related to what they are currently studying.