Keep it simple, 3 camera bodies I'd consider too much weight, certainly not travel light.
I'd take the M7 with a lot of films, 2 large plastic zip-lock bags will carry all films (without canisters). Your wife can take the M8 for instant feedbacks (that is assuming your wife knows less in photography than you, or switch the camera the other way around-🙂
In any case, you don't want to check the pictures en-route. Among all the planning, reading travel guides, going out, moving around, you don't have time to edit the pictures. A HD without LCD screen will do just fine, I'd highly recommend NEXTO with a reliable 100GB hard drive, I never loss a single picture.
I will not travel with expensive equipment like laptop (except cameras) b/c it weights at least 3 pounds, and there is no need for instant editing, more worry about the security anywhere you go.
Have a pen and a well-binded small writing pad, writing on a piece of paper is better than boot up a computer in public places.
One last tip, please loss all electronics to the best extent you can because you will have to worry about juice up batteries on daily basis.
I am a hard-core backpacker. Redundant and backups are way over-rated b/c s*t happens, whether you have one backup system or multiple systems, all can be stolen, robbed, or other unpredictable situations. Keep it simple, if you like the destinations, you can always go back in the future.
Good travel...