That is pretty small as far as reflectors go, so you will be limited in part by that. A few obvious examples spring to mind: a before and after portrait for example, with the sun (if you are lucky!) being behind the subjects head and a reflector used to 'fill' in the face. If the reflector has two coloured surfaces, try each.
While you are not directly modifying the light, but rather making it work for your subject, you could demonstrate the ways in which architcture and/or nature themselves modify light. Take for instance a portrait under sunny conditions on open ground, at midday; the subjects eyes might appear quite dark, with harsh shadows being cast from the nose and other features. Then move the subject under a tree or into the shade from a building, and demonstrate the way this can diffuse and soften the light to create more flattering imagery. This could be extended to using say a large white wall as an environmental 'reflector'.... position the subject facing the wall and pretty close to it. Vary the wall/subject distance and shot some examples when they are well away from the wall.
Also bear in mind that the light from a diffuse light source (i.e. a reflector) will fall off quite quickly.
Good luck and experiment widely. There is a lot to be said for preparing these examples in advance, but approach each location with an open mindset. | 
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