Hi Leah,
Your trip is coming up quickly as it seems it was only the end of school and now school is back.
While some nine year olds still enjoy a children's menu, some would like a more adult menu. With the Disney Dining Plan, you can upgrade your daughter to the adult dining plan. You would need to purchase her an adult park ticket which could then have the adult dining plan added to this ticket. The cost varies depending on the type of park ticket you purchased. The cast members at 407-WDISNEY can help with pricing.
If you choose not to upgrade your daughter, she could eat off of the adult menu at restaurants where a child menu is not offered. In addition, all food at a buffet is available to any guest.
If you do choose to upgrade, make sure only her park ticket is changed to an adult and no airline tickets. You would not want her to be listed as an adult on an airline itinerary as she could be seated in an emergency row which she cannot.
Wishing you a magical vacation!
Beth