One "practical" consideration that argues for CG over Jiko with kids. At least as of the time of our last visit, several of the bigger tables had no tableclothes, and just granite or some other stone.
If our kids are any guide, even well-behaved children tend to drop the occasional fork and, at least in our case, replace glasses and silverware on the table with a bit less subtlety than grownups. At CG, those little sounds are muffled by the tablecloth. At Jiko, they (in our case at least) tended to get Mom and Dad nervous and force us to wonder whether our crew was being at all disruptive. I'm sure it was fine, but during the meal we took note of the fact that tableclothes are a parent's friend at fancy restaurants.