Should I share a scan of my published paper with an academic in my field?

Of course send the post-print. Why does it matter that it doesn't have the right page numbers? Presumably, your colleague wants to assign it to his class because of its content, not because of its page numbers! Send a note with what the proper citation information would be, in case anyone wants to cite it, or better yet just write that on the top of the document ("Please cite this work as: ...").

Why not send it in it's best form, since students are going to be using the information you wrote in it for academic purposes. I think the journal guys should not mind what and how any academic work is shared.