I'd like the ability to also enter email addresses that I would like updates sent to when I make changes to a gallery or add images to a gallery. If the users/clients would like to subscribe to a gallery I would like them to have the same ability.

If I understand this correctly I think it's what I would also like. I would like the ability for me to enter email addresses that would be notified by email with a link to the gallery/image that I've uploaded to my site. The ability for users/customers to subscribe to this feature when I make changes would be great too.