Now that you've theoretically been practicing sit with your dog every day for more than a week, let's go ahead and introduce down. Training your dog to lay down is interesting because (in my experience) 50% of dogs want to lay down and be mentally checked out, the other 50% would much rather obstinately operate on selective hearing and well not lay down.
Much like I explained in my "The Sit" post, this is a command that different trainers all have different approaches and opinions on. Dog obedience instructors I've had despise the use of food in introducing a command because they usually think it's distracting. Personally, I want my extremely food-driven dog to think of laying down on command fondly. Praise will work just fine if your dog is attentive and listens well.
To begin with have the dog sit next to you in a heeling position. Then take your right hand and step in front of the dog and squat down and hover your flat hand in front of the dog about a half foot above the ground.
Kneel down with the dog while saying "down" (if you want the dog to be on a verbal cue...you can just stick with the visual hand signal). When the dog lays down completely reward him/her.
Other sets of instructions for how to train your dog to lay down are Dog Training Central and Petplace. For trouble shooting I recommend visiting The Dog Guide.
The 2.5 week old litter has their eyes open and are starting to play and develop personalities.