Yes scan them all in a single scan, Photoshop has a feature the will find the image straighten the and put the into separate document. I don't know where the option is I don't have a scanner however I know it is in Photoshop somewhere.
Help showed me this
- Crop and Straighten Photos | Planet Photoshop
Photoshop CS includes the Crop and Straighten Photos feature. It enables you to
scan a number of images at once and automatically separate that single scan ...
It in menu File>Automate>Crop and straighten Photos
- Photoshop Help | Crop and straighten photos CS6 - Adobe
Use the Crop tool to crop and straighten images in Photoshop. The Crop tools in
CS6 are non-destructive and you can choose to retain the cropped pixels to ...
I do have a camera and use it to copy. Take Photo in good sun light and find I use the prospective crop tool for there may be a problem having the camera positioned in a pallale plain to the photo..