Existing page list as taxonomy choices

This is what I want to do– I don’t know if I’m just not searching the right terms, or what, but I feel this can surely be done.

I have a bunch (150+) pages that are child pages. For clarity’s sake, the details: The main page is “Sponsors”, and then all of the pages under it are the specific sponsor companies. They have their own little page with details and whatnot.

What I want to do is make posts, and have a taxonomy choice that is basically a category-style (tickboxes) of all of the sponsor pages. So not *every page* (but I guess if that’s what I can get, that’s okay), but of every child page to sponsor.

Eventually I’d like to then, on the sponsor page, have a list of all of the posts that contain that taxonomy.

I don’t mind doing the coding myself but I can’t figure out which direction to go in. Any help would be appreciated!