@Michael-and-Amy0 I didn't mean to imply that you were trying to impose demands on guests. But you have to mention this in your listing information. I'd put it right near the top of the listing description, as in Please note: Our county requires..."
You can just remove that from your listing info when it's no longer required.
If you only mention it to guests after they book, or send a booking request, you'll likely end up with some angry guests.
As far as how to send it, I think you can attach documents to Airbnb messages ( I've never tried that, it's a relatively new feature), or email it to them.