Okay, I partially figured it out - that is, shattering interior faces resulting from a solid shatter. I figured out how to use a group to affect the vertex color of the interior faces (using face area), then applied a scatter with "Use Vertex Colors As Mask" enabled. Shatters nicely.
I wanted to merge the verts on the second shatter to avoid any split geometry from it down the road. So I used an ever-so-slight distance value for the first shatter, then plugged in a polyMergeVert after the second shatter, using a smaller value than that ever-so-slight distance. If there's a better way to merge those verts properly without resorting to a distance trick, I'd like to know it!
So I think that was the easy part.
Now how do I get a peak node to deform only my shattered interior faces? The vertex colors from earlier in the network don't seem to stick through the shatter process, otherwise I could've used that probably.