Those are pretty good exercises; doing all of them might be a little bit of overkill. They will challenge your abs well.
When you're in the gym do work on the swiss (resistance) ball as well. When doing abdominal work on the floor you hard target only your abs; when you're on the swiss ball you are able to work on balance and core stabilization.
I set aside 2 days for upper body, 2 days for lower body and 2 days for core/ab work. My core/ab days typically consist of 2 - 3 core exercises and 2 - 3 hard target ab exercises.
