I live in Thailand: hot, humid enough and beach salt air. Grant gives good advice. Will your guitars be in aircon or at least somewhat dehumidified room(s)? My Tacoma jumbo's top swelled up so much almost unplayable... settled down later... I don't use aircon much as I wanted to (and have) acclimated myself to climate here. Unless you isolate away from humidity, your acoustics will get a somewhat "wet cardboard" quality of sound.
Strings: I don't know about string prices in Okinawa, but on my trips to USA I do bring lots of strings back with me. Enviro packed or Elixir (only coated ones t