Yes, if you each have a Disney Chase Visa, then you each get a picture (we went to the session with my sister and her family and had our picture taken all together and each picked our own picture for free). They give you a coupon for each VISA card when you enter the session.
The characters change all the time. They won't tell you who is inside (probably so no one gets disappointed if someone goes on a break). We have been there on two separate trips. The first trip we had Mickey, Minnie, Donald and Goofy. Our last trip it was just Minnie, Donald and Goofy.
It was so cool. We were in there about 10 minutes and the characters were dancing with the kids and goofing around, very unstructured.