When you export the site, the images are automatically reduced to 96dpi. You can always go back in and replace and rename the exported images with the actual full resolution images, but it seems a bit over the top, unless the photographer wants people do download the images. Also, if the photographer uses the actual resolution images, the images can be downloaded and used for print by unscrupulous persons.

You could publish a page for the photographer to review with pairs of images at 96dpi and full resolution to demonstrate that there is no visual difference.