I think you'd be better served by the 16-35mm f/2.8. 14mm is SUPER wide on a 5D3 and if you're taking shots of people then the centre of the frame is really the only useful part due to the extreme distortion.

If I were using two 5D3 bodies I'd run around all day with the 35mm f/1.4L on one and the 135mm f/2 on the other. Brilliant combo. If you've only got one body then I agree that the 24-70mm f/2.8L II would be a good choice but a fast prime should be in your kit somewhere.