Thanks to all of you, and especially those who weighed in about the bottles. You didn't all agree with each other, and my path is still not entirely clear, but hearing your opinions made me feel a lot better about both options. Sometimes it's very helpful to get an outside perspective, and it's also reassuring to get confirmation that the answer isn't obvious. Sometimes I wonder if I'm just getting myself worked up over nothing.
In response to Jenn's comment about waste management--excellent point. Their waste management is dreadful. They typically burn garbage or just leave it in piles to "rot" (which of course plastic doesn't do, so it eventually ends up in the river). It's pretty horrible. However, since their solution to bottle feeding is buying plastic bottles, my donating a few won't change that equation. There is an active resale market for usable items, though, and extended families share and support each other, so if I give my bottles to someone, they are likely to be used for many years to come by a variety of different women. Surely that isn't any worse from a waste management perspective than going into a Korean landfill or incinerator now.
For the record, Mystery thinks it's a no-brainer and that we should give them to the villagers.