The 1D Mk III has a 1.3x crop factor, so the field of view will be roughly equivalent to 40-135mm on a full frame camera. I don't think that's wide enough for general use. Unfortunately the 1D series don't accept EF-S lenses so it's not obvious what you could use instead as a 'walkaround' zoom.It's a bit difficult to give a recommendation without knowing your budget but I think the consensus would be the Canon 24-105mm L lens.
The 1D Mk III has a 1.3x crop factor, so the field of view will be roughly equivalent to 40-135mm on a full frame camera. I don't think that's wide enough for general use. Unfortunately the 1D series don't accept EF-S lenses so it's not obvious what you could use instead as a 'walkaround' zoom.for