There is a short article on Wikipedia on moral realism, and if we wish to engage others in philosophical discourse I do think it’s worthwhile to read these kinds of things.
As for humanism, it generally means secular human values as opposed to religious values, and includes many non-supernatural philosophies and ways of seeing the world (ours, the objectivists, the existentialists, etc). I had been a Secular Humanist long before I was Epicurean, and this has always been the community that I’ve found most open to us as well as atheists.
Same as above, to reach people with an Epicurean message, it’s a good idea to speak their language so that they can find something in common and hopefully dig deeper. The alternative is never to engage people, or to do so with obscure language or in a manner that they can’t relate to.