I've also just acquired a GoPro for recording the period around totality in 4k. I doubt it will be of exceptional quality in the low light conditions, but hopefully it should suffice for getting the crowd reactions and changing appearance of the landscape and sky. Mainly I just want something I can very easily set up and forget while I take some close up shots with the DSLR.
Wide angle video is a good idea precisely because that can be set up in advance and you don't have to mind it during totality. It records not only the crowd, but also the shadow as it moves across the sky. One thing to have in mind about the low light is that it can confuse the autofocus, so if possible, fix it to infinity.
I set up a GoPro during the 2015 eclipse, but when I tried to turn it on, the display was extremely sluggy (about 10 seconds to show a change) and the camera died when I tried to record. I had forgot to keep the battery warm. Fortunately, I had a second camera, but only 1440x1080i resolution, which worked until a few minutes past totality when the cold also killed that camera. In August we wont have to worry about these things, though.
The most important thing during totality: Don't forget to watch the totality! There will always be a many other people who will take better photographs anyway.