AHA!
I was misled by an earlier post, and looked under File -> Automate.
Now, there is something I can't seem to make this tool do.
It does fine at taking an entire directory of .TIF images and making a new directory of .JPG versions of all the files, and can even constrain the maximum pixel dimension (long side), change color space to sRGB for web viewing, and also adds my copyright notice to the exif.
This is all FANTASTIC!
What I can't seem to make it do is to also make the ppi go from 240 to 72 for web viewing. I figure a full-sensor image would end up about 8" wide at 72 ppi and 600 maximum width, which should be great for web viewers to look at online, but not worth stealing/printing, because 72ppi is way too grainy. At 240 ppi, the 600 pixel-wide images are more like 3" wide.
Any ideas? Mayne I need a separate action first, to change all the ppi settings?