A practical approach is to use an online photo-sharing or gallery service for the review stage, then copy the useful comments into captions/metadata before you archive the files.

Based on the suggestions, Flickr is a strong fit for sharing lots of photos and collecting comments efficiently. It’s built for large photo libraries, makes uploading easy, and supports comments on each image. If you need more control, a WordPress gallery can also work, since each image can have comments and those comments can be extracted later from the site database.

Facebook albums can handle the commenting side too, especially for family members already on Facebook, but preserving those comments with the files later is likely to be more manual.

The key point: comments from these services usually are not automatically embedded into the image files. A reliable workflow is:

1. Upload scans to a gallery service.
2. Let family review and comment.
3. Edit/curate the useful information.
4. Copy that information into image captions or metadata before burning to disc.

If long-term preservation matters, don’t rely on the website alone—store the final identifications in the files or alongside them.