Bring a good water filter and a steripen, if the water is clear use the steripen and if cloudy use both. I understand you have bottled water but sometimes that stuff runs out. Don't eat food that isn't cooked, raw verifies etc are a good way to get the trots bad. If it's something that you can peel like an apple or carrot it's a bit safer. You'll win big points by eating like the locals as much as possible, food is one of the universal interests for all people and a good way to get on good terms with each other.
Bring Gatorade. Go to the world health organization website and look up the place you're going to and they will recommend the vaccinations that you should have and I think they have a first aid kit list.
Bring, Imodium and antihistamines ( the good ones) , cortisone cream for bug bites and insect repellant. I'm not sure what the bugs are like ther but if they're bad look into permethrin treating some of your clothes but not all because you don't want that stuff on you more than necessary. Maybe a permethrin treated bug net for sleeping under. Antibiotic eye drops and ask your doc for a multi spectrum antibiotic, he'll know what to supply.
Probably a good idea to bring some elcheapo knives, multitools etc. for trading. Candies for the kids and jewelry for the moms etc.
Sounds like a cool gig!