Definitely no1. Keep the 35 L, buy the flash, and wait until you have the money for a WA zoom. The 16-35 will not be able to supplement the low light abilities of the 35 1.4 (not even coupled with a flash). And a 17-40 for landscape will do just fine, later on.
trade 35L for 24-70... how often do you really need wider than 24mm?
that's really question to yourself.
Otherwise, 24mm to 70mm @ 2.8 (31mm to 91mm eqv ) has pretty good converage.
ISO 3200 at 2.8 might work in many indoor and low light situation.
Sell 70-200 2.8L, buy 70-200 f/4 L + 17-40L and a flash. When you will have the money, you will be able to upgrage to the 2.8 versions of these lenses.
Otherwise, just rent a 16-35 for the trip and you're set. Do not sell the 35 1.4 as you may need it.
I have an 24-70 2.8L and a 70-200 2.8L on a 1D MarkIII I wish I could buy a 85 1.2L and a 35 1.4L for low light noise free shots DO NOT EVEN THINK to sell 35L you will regret it.
You're asking us what focal lengths you're going to shoot at. We of course can't say, only you can. But, for general/low light shooting the 35L on the 1D3 is a remarkable combo. I would keep it and add a 17-40 for wide angle/landscape if I were you. But do you need a flash right now? Are you shooting a wedding or something?
I don't know what you plan on doing with the photos but I would never take my MKIII and lenses on a 2 week skiing trip. I'd get the G10 unless I wanted to make some very large prints. I got a G7 for exactly this reason; travel and shots that I won't blow up beyond 8x10. I'm sure you could get 11x14s out of a G10. There's not a lot of detail in snow and mountains.
I prefer something I can pull out of my pocket and use on short notice rather than pulling an MKIII out of a sling or backpack. You're not going to ski with the MKIII inside your jacket. Even if it would fit you don't want the temperature change and condensation from sweat when you take it out. I've taken a ski trip with my 20D and 16-35 and it was a real pain in the neck. Add the bright backgrounds and you need a flash to fill in subjects on the snow and you don't have a flash. You'll get a lot of use out of a G10 during and after the trip Take a bunch of sd cards and you can take movies as well.
That's what I would do but I don't know what you want to do with the prints.
my recommendation sound silly, but can help in your tight situation
buy used EFS18-55 & Modify it (will cost $50 for the lens and $11 for modify it, or you can cut it and itll cost u nothing to modify it), and buy tripod if you dunt have it. If you still have spare money then you can buy external flash 430 or 580 (dunt forget to buy strobes, it makes lot different)
for landscape you will be at aperture 8 or smaller (the diff between cheap and expensive lens is minimized).
24-70 f/2.8 is nice wide on a full frame
but 24-105 f/4 I heard is sharper than the f/2.8 and it has a more useful reach and has IS.
17-40mm L is a nice, sharp lens for Full Frame Wide Angle landscape and with the CAD as weakened as it is, you'll get that lens for as much as a used copy of it in the States. I know cuz I just bought mine in Canada from Aden.
