I have a very similar setup, with 4 different machines and a few different libraries.
The Library format is different in MC14 and is not backwards compatible. My suggestion would be to do a limited initial roll-out on one machine, with a copy of your MC13 library. Do not point it at your "production" MC13 library, but point it at a copy of it stored elsewhere. MC14 will upgrade the library to the new format, but will import all of your existing View Schemes and data.
Test it out that way. Test iPod syncing. If something doesn't work, you can always open up MC13 again and re-sync the iPod. Once you're satisfied, drop the money on the upgrade and THEN roll it out to your full network. In the meantime, keep the other machines using MC13. When you're ready to do the roll-out, just delete your MC14 testing library and point MC14 at the MC13 library locations (after making a backup) and proceed from there.
Make sure to keep a backup copy of your old MC13 library in a ZIP file, just in case. You won't need it, but that's just good sense. That's the way I upgrade my library to each new major version of MC. I believe if I look through my archives, I still have the copy of my MC9 library in a ZIP file, accurate up to the last time I ever opened MC9 up, and so on and so forth up through the last build of MC13 I ever used.