I’d be worried about keeping the bearings clean, so you’ll want shielded bearings just for an added layer of protectio. After that, the next choice might be silicone vs pads, as well as how much of either. Then, strings. Wow, how to stock up on that. How many strings to get?
Another yoyo store sells small glass jars for bearing cleaning. It might be good to get one of those. A container of 100% pure acetone would be another supply, that should last you a couple of years worth of cleaning. To lube or not to lube is your next choice, or to Dry Play. Also, what ratio of bearings to yoyos should you maintain. 1 spare bearing for every 10 yoyos? 20 yoyos? Are you going to standardize with C bearings? Any loopers in the mix? Fixed axle?
Metal, plastic, your choice. I’d say
All I will say is that my experience with Africa is second hand, and what I’ve heard isn’t favorable. A sister in law had her laptop stolen, and when she left the area for a trip, the house she was in was broken into and raided. Security might be a concern. Peace Corps too. She had to bug out of Zambia due to warring in the area. Everywhere she went, nobody made an effort. They expected the Peace Corps person to do it for them. Hopefully the mentality has changed. I doubt it.
When I was in Vietnam, I had some yoyos need pads replaced since the humidity caused the adhesive to fail. In one, a Fiesta XX, flowable just wouldn’t stick due to the celcon.
I don’t know what your play habits are like. This only helps with string wear. I’d say 1000 strings should do you good, but maybe 500 is more realistic.
Other than the warnings for “harsher weather” and you’re planning for 2 years, I’d say stocking up ahead of time is the biggest concern. Good maintenance is good maintenance.