My son went to Simba's in I think it was 2002 or 2003, can't remember. He was 5 I believe at the time.
He REALLY liked it. I'm not sure that older kids would rave about it as much, as most of the children in there, toys, furniture, activities, etc. seemed geared toward the younger ages.
The ladies working played with him, gave him lots of food he liked, got him interested in various board games with other kids, etc.
Simba's has a window out onto the main Arusha savannah, too, which I think is way cool!