noob here i want the balls to react and move a bit when the cube goes through them.
have you remembered to tick animated in the rigid body of the cube. As the picture shows.
I can do a brief tutorial to show you but it looks like your nearly there. By ticking the animated this allows key frames and rigid bodies to be used together.
check out my football tutorial might look wicked with more detailed balls https://www.youtube.com/watch?v=-Y7TZb_PDUg&t=810s
balls0001-0250.mkv (1.2 MB)
like you concept with different shapes might look good are you doing a tutorial OR is it for something else.