I had the same question with regards to uploading photos from the gallery. Based on the mistakes I made, it appears as though the pictures you upload into the gallery make up the gallery of photos. There is no way to choose groups of pictures in your gallery. It’s all or nothing. And, I learned (the hard way) that once you upload a gallery to a post, if you change the pictures in the gallery to add to a different post, you end up changing the pictures in all posts. Does anyone have any other ideas??? It sure would be helpful if we could create different galleries that we could simply upload to our blogs. It’s much faster than uploading one picture at a time.
With regards to blog sharing, all you need to do is add the Subscribe widget to your sidebar (which I think you already did!) and then parents, teachers, and other classes (once subscribed) will receive an email each time you publish a post.