larillion,
Gretchen (DD8) and Rachel (She is a friend we made on the Disboards) have been writing each other. So, I am sure they would love to have your neice join in. I will send you a PM.
I have never done Dolphin on Disney, but I have on other cruise lines and I loved it! I have scheduled to take my girls (DD11 and DD8) I think at 12:30...but not positive about that. This excursion usually sells out, you get in a small tank, your girls are young so you would have to get in with them, and the dolphins swim around and play with you...it really is a neat experience.