I dined at Brown Derby with a Fantasmic package in September. The Brown Derby is a great restaurant with top notch food and service. It's also pricey, but the Fantasmic package allowed us to save some money by ordering whatever we wanted with one fixed price. The restaurant has an upscale interior, but it's in the middle of a theme park so it is not too stuffy or unfriendly towards kids. I think that any reasonably behaved child would be quite welcome at Brown Derby.
As you probably know, the Fantasmic seating offered by the package is located at the far right of the crescent shaped arena. The seats are good, but dead center would be better.