The 14mm f2.8 has a LOT of distortion (mustache on FF, barrel on APS-C). It's a super sharp lens but not great for video unless you avoid straight lines. I far prefer the 14mm f2.8 L II (which is not as sharp) for video on FF, since it has almost no distortion, and the Tokina 11-16mm f2.8 on APS-C (also borderline usable at 16mm on FF, but I wouldn't get it for the 5D, admittedly). I use a 17-40mm f4 L for FF and am not wild about it, but it has less distortion than the Samyang and it's easy to find cheap (but f4 is not great). There's another nice UWA in this range that I'd recommend but I'm currently trying to snipe on on eBay. I recommend trying the Samyang before buying. Great lens, but the distortion might be a dealbreaker. It was for me, but not for others I know and I have seen nice footage from it.
Action can be anything from UWA to telephoto, imo. But imo wide is more interesting than long though near-orthogonal action pans can be really sick sometimes. James Cameron mixes a lot of UWA and telephoto, so does John Woo. But long lenses are more useful outdoors, where you have the light for tons of stop, so even the 70-200mm IS is fine whereas UWAs can be useful indoors, too, so speed matters.
All the 50mm lenses are good optically. The 50mm f1.8 unfortunately has bad bokeh but it's fine otherwise. I use a 50mm f1.4 Nikkor AIS and like it a lot...plan to also get a 50mm Samyang when it is released. The Zeiss is probably better than either, but not by a lot. The build quality should be amazing, though, and pulling focus nice and easy. Not a bad lens, just depreciating returns. Imo, the Samyang 35mm and 85mm are amazing for video (about to try the 24mm--we'll see).
The old 24-70mm is worth considering, too.