I might say Hollywood & Vine. For breakfast and lunch it's a character meal with Playhouse Disney (or Disney Jr, I guess) characters, and it has to have kid-friendly food.
For non-buffets, both 50s Prime Time Cafe and Sci-Fi Dine-In are supposed to be kid friendly. But when I was a lot younger, I remember not liking the waiter's and waitress's shtick at Prime Time (no elbows on the table, you have to finish your plate or else no dessert, etc). The food there would definitely be kid-friendly. Also, I haven't been to Sci-Fi in a few years, but some of the movie clips they play might be scary to a really young child (they're all meant to be silly sci-fi things, but some of them look like they're from horror movies).