No, there is not. Apple may be able to help you gain access to your son’s Apple Account, and even to clear the Activation Lock on the phone. However, if you do not know the passcode, there is no way around wiping the phone, including all of the photos stored on it.
Hopefully your son was using iCloud Photos, or was making iCloud backups that included photos, in which case the copies on iCloud could survive a wipe of the phone. You could access photos in iCloud Photos even before resetting the phone; with a backup, you would need to restore it to a phone (wiping the contents of the phone) to see what was in the backup.
How to request access to a deceased family member’s Apple Account - Apple Support