Helen
I like your approach. I taught myself how to play guitar and I do everything wrong (including writing songs). I wished I had done everything as correctly as it should have been done when I first started and learned proper techniques. Anything that gets them to start thinking of structure I think is a nice approach. Me I find a melody in my head and then do the words. Sometimes my phrasing isn't great and I am trying to work on that. A little better structure may make a ok song a good song. Nice idea I think. I once read that experience is a hard teacher first it gives you the tests then it gives you the lessons. Doing it my way was and is full of tests then lessons.

Dan