On the where to use the trashbag question... I suppose that depends on how long it has been raining. If it will rain, I put a moisture barrier on the roof; if it has rained but won't, I put it between me an my ground padding; it is raining, has been raining, and will keep raining, I put me in it. :P I'd leave it up to your kids, this is a lab, you're supposed to learn by error.

How bad do you find their attention span? I've known a lot of kids (late teens, college freshmen) with true ADD and ADHD, along with Asbruggers, and I've found that they can pay attention if you capture their interest in most cases.