Chef Mickey's is definitely on my "only when a travelmate insists" list.
And generally, in the past few years, when that has happened and we go, they end up feeling underwhelmed by it.
The food is buffet standard, not bad, not great. I say it's a bad sign when someone asks you what's good, and the only answer is "the mashed potatoes."
The whole place is tired, and rightfully so since it remains so overhyped and constantly at capacity. The service staff probably try their best to stay positive and helpful, but generally are forgettable or downright bad. The restaurant itself has that overworked, needs refreshing feel which can make it seem dirty. And parts of it are downright filthy, not just run-down, including the serving line which seems always to have caked-on food on it and various parts of the walls, floors, and chairs which bear perpetual handprints and dried-on food as well.
That being said, to the OP - a 4-year-old isn't going to notice any of this, just that Mickey and his other buddies are there to hug and wave at.
Probably not as the food wasn't stellar but just decent and it's really expensive. I think $60 per adult + tip and drink.
Just to be clear for those not accustomed to Disney dining: standard non-alcoholic beverages such as soft drinks, tea, and coffee are included in the price of the meal as posted at buffet locations and are not an additional charge. Alcohol, where available in a buffet restaurant,
is charged separately.