The 5D Mark III and the 1Dx have very similar image quality (excellent!) and autofocus systems. Either one would be a significant upgrade from your original 5D. Like moving from an old Chevy to the Space Shuttle. The 1Dx is built to withstand much more abuse than the 5D3, including bad weather, sand and dust, and constant pounding. It also has a built in vertical grip, and can record audio tags associated with your photos (very useful for captioning.) The price difference for these features is, of course, also significant.
The new 6D is also a full frame camera with excellent image quality. It has a simpler autofocus system much like your 5D. It's smaller than the others, and much less expensive -- under $2K. It would be an excellent upgrade from your current system, though not as revolutionary.
For the cost of a single 5D Mark III, you can probably buy a pair of 5D Mark II cameras in good used condition. The 5D Mark II is still a very good camera. It has the same AF system as your current 5D, but with much larger files and better high ISO image quality. (I would not shoot a paid assignment -- especially a wedding! -- without two cameras, and preferably three since I am known to screw things up.)
Your lenses are fine, the 24-70 in particular is a good lens. You may wish to look at something like the 135/2 or maybe a 70-200/2.8 as a longer lens which can be useful at weddings.