It would be reasonable if they can sit thru that long a meal w/o becoming--how shall I put it?? --agitated.
We always see kids at JIkos, but unfortunately, not all are well-behaved. You know your kids, so if you have any qualms about their sitting thru a long dinner, I'd suggest the kids stay with the grandparents.
And by well behaved I don't mean sitting still with their hands folded w/o saying a word. Normal kid" chatter" is certainly expected. But not the running around the restaurant yelling and screaming, throwing food at each other, walking to other tables just so other diners can see how "cute" they are, crawling on top of the table, etc etc All of which I've seen any #of times at WDW restaurants and would certainly be inappropriate at a place like Jikos.