I'd check in the Touring forum for optimal advice. But....
Since you're traveling by boat, I'd bring more stuff rather than less. Lots of spare tubes, a few spare tires, I'd also get extra spokes, extra chain, lubricant and maybe even an extra derailleur. But really, given the nature of the trip, if one or both bikes gets stolen or utterly destroyed you can always get another bike.
If you're worried about the brakes, it looks like the VIII or whatever can be equipped with disc brakes, could be very handy for the rougher roads down there.
I wouldn't worry too much about the tools. A typical multitool will be fine, just get one with a chain tool. Keep it in a ziploc if you're worried about it getting wet.
Also I suggest you email Downtube and find out in advance if they can ship any proprietary parts (e.g. handlepost), or even a full bike, in some of those locations.