Here is another project we taught the kids at my old non profit. This is a carnival shooting game. Some core concepts were sprite transforms, how transforms can fake perspective, sprite collisions, game aesthetics (like leaving bullet marks on shots on the wall), and then falling objects with gravity that you could "hit" and have them react by going up.
https://cloud.snap.berkeley.edu/project?user=nedens&project=Carnival%20Shoot
how old are these kids???
those games are pretty awesome. Nice design 
I was teaching kids 8+. We did the project over three 1 hour classes.
Each class we taught some core fundamentals in programming and then implemented it with a practical usage in the game we made for the month.
These weren't advanced kids or anything, some of them had never programmed. The block programming really makes things super simple. For this class if I remember right everyone had already taken a basic Snap! class so they understood the interface. The graphics were all provided for them for the class (we also did 3d modeling, 3d printing, arduino programing as well). I always believed programming was available to be grasped by anyone you just have to attack it in smaller bite size bits and then build up. So that is how I taught the classes.
Thanks!
Wow! These games are professional quality, man!