Expanded Distribution vs. Amazon

I wrote a short booklet (lead magnet) about a geological disaster that shaped the PNW into the landscape that we see today. While I’m offering it free on my website, I’d also like to make it available to some of the tour groups, visitor’s centers, and organizations that regularly teach on this event.

It’s super short. Between my fiction piece and a scientist’s non-fiction article, it’s only 28 pages. If I select “Expanded Distribution” (which means other people can buy it wholesale, right?) the minimum price I can charge is 5.75. That seems expensive, especially since my purpose is to build an audience. But if I select only Amazon and sell it at 3.85, won’t the visitor’s centers be unable to redistribute it?

So…

Which should I choose? Can I change my choice later? Also, are there strings attached when choosing an Amazon ISBN number?