I would pull the lead-acid battery out of the Mac Portable, Apple says to store it with a 50% charge (if it still holds a charge .

As far as the logic boards and other PCB's -- AVOID MOISTURE! Use moisture sealed, vacuum packed bags. Moisture causes corrosion, de-lamination, cracking, etc. Ideally you should get a storage space in the high desert.

As with preventing leaky caps, you could always consult with NASA and see how they handled long-term storage of their electronics circuitry onboard their Deep Space Exploration Spacecraft ...