Hi David, you might also consider taking a water purifier with you such as the First Need Deluxe. It removes bacteria, cysts and viruses from water without requiring chemicals or electricity. It's light and compact – and the water tastes like water not like tablets. I was in the Solomons some years ago for awhile and had to use the tablets. I don't know about you but I found them unpleasant and tedious – I wish I'd known about the First Need then.
If I'm not violating any rules by mentioning a web site you can see one at: http://www.crystalclearwater.com.au/product/320000

All the best on your trek
Cheers
Michael