We all enjoy finding excuses to buy new stuff. IMO, if there is nothing wrong with your current camera and lens, and if you are happy with the 35mm field of view, why waste money changing? Sure, you can get the 5DII, or the 35L, or both, but again, the 5D is still a very good FF camera, isnĀ“t it? And, for a FF camera, it is actually not that heavy, especially mated to the 35 f/2.
Now, of course you are free to do whatever you want, so once you make up your mind that you "need" a new camera and/or lens, fine, there are inumerous possibilities. IMO, for this trip of yours, it makes sense to:
1. Either stay with Canon, and upgrade within your comfort zone (same type of camera and focal lenght), or
2. Change systems so that you and your wife use the same brand, as a backup.
Again, and IMO, if you enjoy using primes, there is nothing better out there than the Pentx K5 and the Limited lenses, either the FA Limiteds, or the DA Limiteds. Sure, the DA Limiteds are not very fast, but they are fast enough, especially with the high ISO capabilities of the K5. A K5 plus the trio of DA Limiteds (15 f/4, 35 f/2.8, and 70 f/2.
will fit in a small bag, and you hardly notice they are there.