I live in New Zealand and am well aware I'll be receiving my rewards later than most (and at a greater cost to you, also). That said my preference is easily you just package it all up once the discs are done and send it to me together. Cheaper for you, more efficient in terms of man-hours spent, packing and posting and less chance of backers needing to futz around with changing addresses etc.
If I can play my download of the game at the same time as everyone else then I'm perfectly happy waiting patiently for the physical stuff to arrive in the post. Same story with Wasteland 2 and last I checked my head didn't explode. Besides I'm 35 years old, I just don't need to hold the loot in my hands to be excited by the finished game anynore, much as my hoarder side appreciates the trinkets still .
Just pass around download links to the strategy guide and lore stuff and we're all good.