You won't be able to charge your iPad 2 directly from the hub. The best solution is to charge a battery, which can then charge your devices. I've used a LimeFuel battery. You'll then need an adapter between the hub and the USB port. I used a Sinewave Cycles Revolution. The thing is tiny and waterproof.
I question your need to use three pairs of shoes. Why not ditch the clipless system and just ride in your sneakers? If you're on a world tour do you really need the minor efficiency gains and complexity added by a clipless system? What's the rush?
You're bringing what seems to be a lot of maintenance equipment for what is supposed to be the most trouble-free hub out there. That's why you shelled out the big bucks, right?
How about bringing along a ukulele instead of a guitar? Or learn to play keyboard on your iPad?
I agree with Max that using 4 panniers + a trailer is not ideal. The idea of using a trailer at all seems inconvenient at best. What if you decide to hop on a bus or a plane? Schlepping a bike and trailer sounds like a nightmare.
I also agree with Max on bringing waterproof booties and gloves, unless your around the world trip somehow manages to avoid cold weather, rain, and snow.