Disposable cameras are actually more expensive and are limiting in terms of creativity. They also usually never have 36 shots either nowadays, usually 12-24. Getting rolls processed outside adds up quickly. But they are good for getting everyone their own camera instead of sharing if your plan is to let them take them home. You can hack a disposable to remove the film it has and put your own in to reuse too which will make it considerably cheaper if you load up with bw.
If your community center has a darkroom make use of it and have the students learn to use it for b&w.
I would recommend you to reread some of your intro to photography books again just to cover yourself if students have questions especially about the many related variables in photography. Borrow photo books from the library and show them examples of great photography and what makes it great. Expose them to varied subjects to and styles, at this age they emulate well. People these days are bombarded with too much visual garbage.
Pinholes and camera obscuras are fun projects, I actually wrapped that up with my students this week. Fun results, we even got older students to sit for a long exposure indoors haha. The most challenging thing I find is that kids these days like instant results, or are used to snapping away 10 images at a time with their cellphones or Nintendo portables and can get carried away and before you know it half a roll is gone dedicated to one subject like a game screen or a computer, or lose interest if they can't wait to see what develops on the film a few days later.