We purchased a photo package, and thought it was very much worth it. The experience of swimming with the dolphins (and the DC experience on the whole) is so special, I wanted to make sure we preserved those memories forever.
Our pictures were excellent quality. For the dolphin swim, the photographers are right in the water (much, MUCH closer than you will be on the shore) so the photos are clear and very close up. I cannot imagine that you would be able to capture comparable pictures with your own camera.
There are different photo packages available for purchase, so you don't necessarily have to buy the most expensive one which comes with the DVD (we didn't). Our package, which was about $159, gave us all photos from the entire day on CD, several 6 x 8 prints, and a few photo key chains. We also were given a free stone 6 x 8 photo frame, but I'm not sure if they are still doing that or not. The largest package, which retails at about $219, comes with the DVD (probably about 30 minutes long....but that's just a guestimate based on the amount of time you are actually interacting with the dolphins), a poster, a scrapbook, and all the other items listed in our smaller package.
For photos taken during the dolphin swim, they are all pre-arranged shots and will be taken the same for each participant.
One pose with the dolphin "smiling" (open mouth):
One giving the dolphin a kiss:
And one of you "swimming" with the dolphin:
Multiple shots of each pose of each person are taken. For the "smiling" dolphin pics, they will also do different configurations for you. For example, we had DH alone, DS alone, me alone, DH & I together, and the three of us together....and at least two shots of each of those, and sometimes more.
In addition to the dolphin photos, photographers can be found in the Aviary, in the lazy river, and in the Freshwater Oasis. All you need to do is go ask one of them to take your picture, and those photos will be added to your CD as well. Here is one we had taken in January 2012 in the lazy river:
I think we had about 45 pictures of the three of us on the CD, and that was before the Freshwater Oasis had opened (so now there's even more opportunity to add more pics to the CD). And with your larger group, you would definitely get some good value out of the photo package.
Hope that helps. Let me know if you have any other questions.