I'd go with one of two schools of thought:
1) get the bike's existing 32H wheels tensioned by an expert wheel builder and use 'em until they are toast. I've abused some economy mtb wheels on a touring/utility bike for a long time after I expected they'd be junk they just keep on trucking.
2) get some hand built wheels with your components of choice - 32H front and 36H rear should be plenty. Go as heavy duty on the rims as you need. LX hubs are a tough low cost choice.
Option 1 is cool as long as your first trip isn't to Outer Mongolia and will give you time to source parts for Option 2. If you don't want to deal with any hassles and/or are heading to a remote spot off the bat just skip to Option 2 and save the original wheels for when you are home and using the bike as a commuter.
safe riding,
Vik
www.thelazyrando.com