If you don't already have a camera brand you have lenses for and are free to choose I would say the best cameras for low light stills are probably
1) Nikon D5
2) Sony A7S II
3) Canon 5D MkIV
Again, how long is the trip as you can rent a D5 for a week for about $350... Could be option... A Canon MKIII I think is about $130 for a week.
Once you pick a camera body then you can nail down the lens. I personally don't have any experience with trying to shoot a wide angle through a flat port but I think you would have a whole heap of problems trying to do so. Anyone here managed to get good results? I am also not familiar with Nikon and Sony lenses so will leave that for the people that are but if quality is key then I would go for a good prime rectilinear lens like the 35MM F/1.4L II if it's canon or possible the 50mm f/1.2L . The worry I would say with needing to use such a wide aperture is getting the DOF you may need.
I would take a guess that your best bet is to shoot with a 4K camera that can also take stills. That way if you are finding that the stills are not working you can still get some footage.
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