This question has some time, but I would like to comment.
In my opinion, the first step would be a batch resize and crop. Do not overwrite the original, but generate a copy instead. There are several programs to do that, that do not even "open" the file.
The reason is that after this step, you can work with smaller-sized assets and not have to drag a humungous file on the next steps, even the planned color adjustments. That is a common task in video editing, so you will have perfectly capable color correction tools on video software. No need to use Gimp.
Even on normal editing, is common to use a lower resolution proxy when editing.
An additional note. 1440x1080 is not a common aspect ratio. Some players or users could be tempted to resize to a more common 1920x1080. So it is better to make that decision yourself.
If you do not want to make that decision yet, In my opinion, is better to resample the photos to 1920x1440px first, and use those to make the video. They are easier to work than the original, and you can choose to crop or not once you see the sequence as a video.
Then you could either crop to FullHD without sacrificing the sharpness, or if you still want that aspect ratio, then resample the video once finished.