It's very important you take them on your days off mate, as this is when the muscles are repairing, and need all the nutrients like protein and carbs' to rebuild bigger and stronger.
Having your morning shake with oats' if you can, as when you first awake your body is in desperate need for some carbs' as it's gone all night without food. Also, from what I've read, protein on it's own first thing in the morning isn't as useful as with a carb' like oats, because the body doesn't absorb as much of it.
Benni.