The next step will be to teach the puppies that they can do something to make the food appear, tomorrow or friday we'll set a small box or tray on the floor and we will click them for every interaction with this box. The interaction can be as small as looking in the direction of the box or as big as stepping into the box but we're not aiming for anything in particular just the realisation that they have a choice and some power.
In training this is known as shaping, you're shaping a behaviour the dog naturally does, it's a fantastic way to teach a dog things like play bowing or walking backwards and there are even people out there who exclusively shape behaviours rather than luring (where you use the treat to guide the dog into a sit, down etc).
Enjoy the video and hopefully I'll manage to get some footage of the pups playing with a box :)