Our kids enjoyed both of those. Chef Mickey's is good regular breakfast food, plenty of character interaction and you get the photo at the beginning of the meal (for purchase of course...unless you have the Photopass Plus then the photo package is included).
Garden Grill is really neat, it rotates and again...pretty regular food for kids. Tons of character interaction at this restaurant, but it's quieter than Chef Mickey's. No photos taken at the beginning of your meal but your server can take one of you at your table if you want one.
Both are places I'd recommend trying at least once, if I had to choose which to try first.....goodness that is hard. I would probably go with Chef Mickey's first though, and then do Garden Grill at a later date.