We bought the full photo package on our last 3 cruises. We took a ton of photos so it was worth it for us. It was even more worth it because they printed the photos and included the digitals on CD. I think on our last cruise, we took over 150 photos, and my wife made a conscious effort to go take photos. Our kids are also young so they loved the character meet and greets, and a lot of photos are from that.
If you're not planning on doing a lot of character meets, and stand in line to take photos, then the full package might not be worth it. I believe there are smaller packages, where you can buy one, or a few photos.