Hi there, Alysse!
Dining with the Princesses occurs at one of three places:
Cinderella's Royal Table in Magic Kingdom,
Akershus Royal Banquet Hall in the Norway pavilion at Epcot, and
Cinderella's Happily Ever After Dinner at 1900 Park Fare in
Disney's Grand Floridian Resort and Spa.
Since you are staying in Magic Kingdom, you will certainly want to try to pick up a reservation at the Royal Table. The restaurant - in Cinderella Castle - serves all day, so you have lots of flexibility with times, even for a midday meal.
And make sure you stop for a photo opportunity with the Princesses! Located in Town Square Theater, just under the archways into the Park, you'll find an indoor character spot in which your little ones can meet several of the Princesses, one at a time. You can be received by Princesses Aurora, Tiana, Belle, and Cinderella, but these are subject to change without notice.
Have a wonderful day!
See you later, celebrator,
-Deborah B.