Keep in mind the pro bodies don't have modes (e.g., sports) like the consumer models. Also with a FF you'll need a longer lens for the same field of view. The 70-200 2.8 is a much heavier lens, if total weight is an issue.
Video works because it's surely using a much lower shutter speed. You won't notice motion blur in frames (photos) when they're whizzing by at 20-30 fps and there's a lot of motion in the video. Also, the video may be shooting at a lower resolution.
You might want to set whatever cam to JPEG+RAW. That way she can have JPEGs, but you can do post-processing on a select few good images in RAW to adjust for levels and do noise reduction.
And remember, at the same ISO and f/stop, a shorter focal range (mm) gives you more light (which equals higher shutter speed). Consider the old "foot zoom" and using the fast and sharp 50mm 1.8 and either getting a little closer, or cropping.
Video works because it's surely using a much lower shutter speed. You won't notice motion blur in frames (photos) when they're whizzing by at 20-30 fps and there's a lot of motion in the video. Also, the video may be shooting at a lower resolution.
You might want to set whatever cam to JPEG+RAW. That way she can have JPEGs, but you can do post-processing on a select few good images in RAW to adjust for levels and do noise reduction.
And remember, at the same ISO and f/stop, a shorter focal range (mm) gives you more light (which equals higher shutter speed). Consider the old "foot zoom" and using the fast and sharp 50mm 1.8 and either getting a little closer, or cropping.
The photos help. To stop action in those circumstances I'd want at least 1/500 second shutter speed and in that light it means running the ISO up to 1600 or 3200 which all but guarantees noise. The newer high end DSLR's like the Nikon D4 are made for that and will get the shots your wife wants but it costs $6k. And lenses are extra.
How bad does she want those photos?