Well, Since you've mentioned this website is for non-profit, I'd like to offer you something great and different. I could offer you WordPress or any PHP based website, just like the others but instead I'd like you to try Jekyll (Google it, if you don't know about it already) Jekyll is a static site generator, it works just like WP, you can add as many pages or posts you want, but I tell you the main difference.
Since Jekyll is static, it's amazingly fast, nothing can beat the speed of a static website, Static websites are Hack Proof unlike WP or PHP based website. It's easy to use and it can be hosted for free on GitHub and as GitHub uses CDN to deliver content, it will make your website even faster.