Neuro just revealed my standard travel gear (though I ended up switching the 5D2 for the 1D4 and only have the MKI version of 70-200mm f/2.8 IS).
I think most people agree that you can't go wrong with the 5D2 + 24-105mm combo. For both 5D2 and 1D4, I'd say that the 24-105mm sits on the camera body almost 90 percent of the time.
Now, I think the second lens would vary depending on your priorities. I use the 70-200 f/2.8L IS as a fast/long distance/indoor lowlight option, as well as the option of popping on the 1.4x extender to get a slightly longer reach if push comes to shove.
However, if you like lighter weight, the 70-200mm f/4L IS would be a better option. Of course, you can still use the extender for this lens.
I don't know about the 70-300mm f/4.5-5.6L IS, but many reviews are saying positive thing about this lens. However, you can't use the extender option for this lens (though I think the size and weight is the biggest plus for this baby - albeit a bit slow).
The 100-400mm f/4.5-5.6L IS probably has the best reach, and with the size approx. comparable to the 70-200mm f/2.8L IS. However, you need to decide if ur OK with the push-pull zoom and lack of weatherseal.
So... if compact travel gear is ur top priority, go for the 24-105+70-300 option.
If you want a balance btwn size and picture quality, try the 24-105+70-200(f/4) option
If reach is your biggest concern, the 24-105+100-400 would be the best.
If you really have to make room for sports/fast action shots, the 24-105+70-200(f/ 2.8L) is probably the best choice (though be warned... your back will start hurting soon).
Now, as an add-on to the above options, you might want to consider popping in extenders (1.4x or 2.0x - ur choice) for better range coverage at the expense of picture quality and speed - though this option won't work for the 70-300mm.
If you choose the slower combos but still need a fast lens option, just get the affordable and fast 50mm f/1.8 - it's small enough to fit ur baggage and something that'll give you speed when there's no other choice.