California Adventure's Ariels Grotto Question!?

At any of the character meals you will need a reservation or plan to wait a couple of hours or more to be seated. Call Disney Dining and get one set up before you even leave for the trip, you can make the reservation weeks in advance. Ask them if you can request a "Happy Birthday" song for her, this may need to be done when you get there though. I don't have the phone number handy but check on the Disney website it is listed there.