There are lots of ways to use toy cameras to teach photography. I don't have a curriculum for you. But, I would suggest using the cameras for different shooting assignments, as you would with any camera. And you can have students try different camera modifications.
Combining toy cameras with pinhole camera photography is a great mix as well.
Using low-tech cameras (whether Holgas, pinholes, disposable cameras, classic cameras, etc) is a great way to focus on image-making via composition, as opposed to being fixated on the technical aspects of the equipment. Also, if you try shooting in a variety of formats (with higher or lower quality gear), you can get a sense of how the same subject looks different when captured by different image shapes, lens types, capture media (B&W or color film, digital, etc). All of these elements can be used for a great class!