First of all, don't stop trying to get 'Ohana. I couldn't get an ADR to save my life, but I kept checking several times a day, and I finally snagged one a few weeks before my trip.
In the mean time you need to secure another reservation (that you will considerately cancel if you get your "Ohana reservation)
We had a hoot at 1900 Park Faire with the step sisters. We were a table of adults, and got a real kick out of the ladies.
Another place we enjoy is Tepan Edo. The Japanese Chefs put on a show cooking in front of you on the Hibachi. Good, but if you have this kind of restaurant at home, its not really worth it.
Maybe, now that she's a young lady of 17, she might feel special with a signature meal. California Grill, during Wishes would be a nice way to celebrate.