Yes! Grandparents and other relatives can save photos/videos as well as delete their own comments by doing the following:
Saving Photos/Videos
・App Version: Open the Album tab and tap a photo or video. Tap the menu icon in the top-right corner, then tap "Download."
・Browser Version: Click a photo or video, then click the "Download" button.
If the Album Admin doesn't want other album members to save photos/videos, go to Settings > Configure Album Details > Download Permission, and change the setting to "Admins Only".
Deleting Comments
*Grandparents and other relatives can only delete their own comments. However, album members not allowed to comment also won't be able to edit or delete their comments. In this case, please contact one of the Album Admins (parent members).
・App Version: Tap and hold a comment to edit or delete it.
・Browser Version: Click the X button next to a comment to delete it.
If the Album Admin doesn't want album members to post comments, please change the settings from Settings > Configure Album Details > Comment Settings.