Check online for the dates you are thinking -- but at least up until 9:45. You will be able to get there after Illuminations (show ends at 9:15ish) particularly if you watch from France or UK area, easy exit, then less than 10 minutes to the restaurant.
Going before Fantasmic also doable. I try to be at Fantasmic at least 60-90 minutes in advance. The walk from Boardwalk is roughly 20 minutes. I would do Kouzzina as early as I could (5:30) -- but I hate rushing dinner.