amckean, I would recommend getting a soil meter. You just stick it in the soil. Very simple and very accurate. As they get bigger you'll be surprised by how much water they can drink. But when they are small they don't drink much. You don't want the soil to stay wet all the time, no air can get down to the roots. Let them dry a little. Then water. Remember they are only 2 week old. Hereā??s a link to check out.

http://www.windowbox.com/products/3-way-soil-meter/

Good Luck