I do like the Machete order (4-5, 2-3, 6), because of the reveal in ESB, then showing Anakin's fall before his redemption.
Putting R1 before ANH, for a new viewer, I think would do them a disservice. R1 shows that they KNOW there's a way to destroy the Death Star, leading to an inevitable conclusion in ANH (I mean, we knew it would happen, but not how). Instead, I think R1 should go after ANH.
I also agree with people saying to leave off TFA. Not because it's bad or anything (I enjoyed it), but because it's not a complete story. While most of the movies (like them or hate them) do stand alone fairly well, TFA leaves you hanging even more than ESB at the end. Let them watch it if they're interested/want to, but save it for last and let them decide.
I also agree with the idea to break it up and spread it out. Overload is never good.