Three types of pictures are taken by Shutters. Pictures with characters, pictures at the dining rooms and formal shots. The last one, is the one you cannot do on your own.
Shutters is prohibited to take a picture with your camera. However, characters are always accompanied by a CM. And the CM will be more than glad to take a picture for you. This would be the only way to get a family picture with them. Of course, there are some CMs that have no clue on taking a picture, but for the most part, you'll get GREAT shots.
Picture at the dining rooms, I've taken better pictures and even my DS15 has taken great shots of me and DW.
Formals is different - these are done on a background (sunset, ship in the back, beach background, or simply white). It's a great opportunity to get them done on formal nights. Other ones are taken with the Captain, and others taken by the grand stairs.
On our first trip, the ship was 3/4 full. Lines were very short (no more than 5-10') so we took advantage of shutters from the get go. On a 5n cruise we had over 100 shots with them. We did purchase the CD and we knew we were going for that.
On our second trip, the ship was full (Wonder) and had over 1200 kids. Lines were extremely long for shots with the characters. And since the trip was less than a year from the previous one, we skipped them. Only a few character pictures. But we did get several formal shots and purchased the 10 picture on CD package.