I'm not pro. A few years ago I was doing some fashion work and was considering the 6D vs the 5DMIII. I went with the latter as I really needed the flexibility of the cross type AF points. That was three years and about 60,000 shots ago. I've come to rely on the power of the autofocus functionality of the 5DMIII for lots of different activities. My sports, ballet, marching band, and zoo photos have benefitted by how I can make it handle action. If you've ever explored the AF functionality of the 7D, you should consider that in your decision.
I admire you've been able to travel around the world. Were I doing that and I was choosing between the 6D and the 5DMIII, I'd go with the 5DMIII. I've done shots with my ELPH 330, a great little camera in its own right. I love my G16 for all of its power. Regardless, were I to be traveling solo and wanted the greatest flexibility, it would be the 5DMIII. I can imagine situations where it would be neat to photograph some local sporting event or some public performance that you're allowed to photograph. The 5DMIII is a beast of a machine (and it's only that, a machine, a tool), but you can do lots of things with it.
On WiFi, the ELPH and G16 have WiFi. Big deal. The few times I've used them for WiFi was when I wanted to transfer a jpg to the iPhone to post on Facebook. (RAW wouldn't transfer from the G16.) That said, there are WiFi memory cards you can get if you want. GPS? My iPhone has GPS. Droids have it too. Again, who cares? I know where I am, and my travels are limited. There have also been GPS accessories you can buy to tag photos, and you can probably get some today. If you're traveling so much that it's difficult to keep track of where you've been, then some form of GPS tagging might be helpful. I know for me that GPS tagging isn't much of an issue, except in a couple rare situations. If I really need to tag my location, I take a photo with my iPhone.
Whatever you do, have fun, take great photos, and post them on PotN!