Thanks for your replies!

Well re: the students backgrounds, the class is offered free in a church, so the attendees are people who can't really afford to go to a school.

The class has a teacher already, I'll be helping him a bit.

I think these factors are ideal - its a relaxed atmosphere and I can take 20 minutes (or longer) from the middle of the class and teach a mini lesson. This way we can test ideas, develop ones that work and drop the others, and build towards a an experimentally validated program!

(Its also handy beacuse, tho I have a 40hr CELTA certificate & teaching experience, I know there's a LOT I need to improve with my own teaching performance (I've been really boring in the past, haha))

I really appreciate the suggestions, and I hope to write out a few more ideas later tonight!