You are going to get a BUNCH of advice. I'll keep it short and simple.
I would recommend the BMW F650GS twin (called F700gs for 2013). It is the same 800cc motor, tuned for torque and better gas milage. It also runs on regular gas..so hi test gas is not needed. It sit about 2 inches lower than the F800GS or the triumph. From you height, I would think it would fit you better...ie both you and you wife should be able to flat foot it vs being ballerinas.
The trade off is ground clearance...but riding two up I suspect you will be taking it easier. I do recommend a skid pan just in case.
I have one myself (due to my 29inch inseam). took it all over alaska, yukon etc this summer. 65mpg when riding under 60mph.
a second choice would be the suzuki 650 vstrom. a little less power, a little heavier, does not handle quite as well...much cheaper, more reliable.
have a great trip