If your going to be outdoors i assume you can step back, so is focal length that much of an issue? I also assume your doing portrait type work, so you would want creamy bokeh?
I wouldn't really use the lenses you've talked about because the the only go to f3.5 and f4 on the wide angles.
Rent a 70-200 f/2.8 IS USM (the newer one to which i have)
I can tell you that he MKI of this lens is brilliant for portraits. In fact, see what fast telephoto lenses you can get. The 70-200 has the perfect focal length, it allows plenty of space for the subject not to feel intimidates, the fast aperture gives great bokeh and works well in low light and the long focal lengths make the images seem more compresses, give a more flattering look.
Here is a list of lenses i would recommend for portraits:
>17-55 f2.8 - only EF-S
>May be a 50 f1.4
>100 f/2 - great lens
>135 f2
>135 f2.8 - GREAT LENS (SOFTFOCUS LENS It allows sharpness to be adjusted, makes skin tones look nicer
> 24-70 f2.8
>70-200 f4 or f2.8 (even better)
If you insist on one of those lenses, i would go for the 17-40, but only because its an L lens 
hi.