For safety...
Make sure you have a helmet for the kid, and consider some bike specific clothing.
I like orange or yellow construction vests. Perhaps not the most popular thing for school, but they will be much more visible than a bike reflector.
I'm often on the prowl for bright colored clothing for when I don't wear the vest.
For dusk, dawn, or night riding, a light will be better than a reflector. I like rechargeable ones that I can top off as needed.