I've also found that it's good to have a conceptual framework that you can tie things to. On Central and Southeast Oregon trips with high school-age students that framework was either how various differences in magma composition and environmental factors interacted to create different styles of volcanism, or how geologic factors (including- but not limited to- the landscape) interacted with the rest of the non-living world to effect the local biota. The conceptual framework I've been pondering for this trip more or less combines those two, and unites them in thinking about the large scale tectonic structure of Oregon: subduction, forearc ridge, forearc basin, arc, back arc rifting, and influences from the Yellowstone Hotspot, which made its presence impossible to ignore in Miocene Oregon. Basin and Range is still a little enigmatic to me, and I haven't seen anything that convinces me that the questions surrounding what drives that rifting have been satisfactorily settled. Nevertheless, it is certainly best explained in terms of tectonics; it's just that there are at least two approaches to doing that, and probably more, in addition to sliding scales of importance of this factor versus that factor.
All that said, here's the outline I just sent to the person sponsoring this volcanic ramble: