There is a tendency to think that only 6v6 play can truly be game-like. This is a failure of imagination, though, and probably also a failure of focus.
Having to work with a group of players at different levels of development and/or skill is a real challenges. Here are some ideas for doing so.
There are a number of volleyball exercises where players start off blind to the ball, then have to find it. Here are my thoughts on their value.