A good way to increase humidity around potted seedlings is to set a couple of seedling pots in a larger container of pebbles. The pebbles should be about fingernail size, and there should be just a small amount of water in the pebble container, enough to create humid conditions but not enough to touch the bottom of the pots to prevent the roots from rotting.
Place the seedlings in a shady area that will get a hint of sunlight. As the water evaporates, simply add more water.
