you havent told us how big the seedlings are...
make sure before you transplant that the seedlings have developed a good root mass to hold the soil together when transplanting, this makes it much easier on you and the plant.
once you set them into their new home you should water the entire pot thoroughly, then wait to water again till the pot is relativly dry, or light when you pick it up. you want to water in well because you just transplanted, this helps to settle in the new plants to the container and also make sure any spots in the soil that are really dry get wet, otherwise the soil may become hydrophobic and not absorb any water later down the road, these dry pockets can cause potential problems and make part of the container unusable for the plant roots.
a small seedling in a 2 gal pot should be able to go around 5-7 days without watering if you water till you have good runoff. (depending on the heat and enviorment too)
overwatering of plants generally happens during the seedling stage when they are in small cups starting off because people think they need to spray the plant 10 times a day and end up drowning it. as long as you water it and leave it alone, dosent matter how much water you pass through the pot when you water, but you always want to try and get a nice even soak of the soil to keep all parts damp and usable for plant roots