In which order R1, R2 and Akito the Exiled need to be watched? I am planing to watch R1, R2 again with Akito the Exiled but will be joined by a person who have no idea about Code Geass before.

I know Akito the Exiled take place between R1 and R2 from the similar question but I have no idea how much they are related to each other in details.

So what is the best order to watch R1, R2 and Akito the Exiled without getting anything spoiled in advance?
Story of R1 and R2 isn't affected by Akito the Exiled enough to be considered a spoiler of any sort. 

AtE is an Alternate/Side-story and thus you can watch it whenever you want, though I'd advise to watch in the release order (and not just for Code-Geass, but almost every series out there) because that's how they are made and that's how you're supposed to be watching it.