To wake up any of the three sleepers, you will have to mind-read them. Each character requires a different item to wake up and each item can only be discovered through a mind-read. So to wake all three you will need three mind-reads costing 300 - 400 each. There is no reward for waking one or two of the sleepers, but if you wake all three they will give you one Malachite Gem.
Furley needs a drink to wake up.
Nightwinkle needs a red apple
Namda needs a health potion.
Afterwards, the trio can be found in Broken Valley village, near the chapel.