As noted above, the waiting is the killer, not the time at the table as once you are seated, in the non-buffet restaurants you are in and out fairly fast (our record in August was 45 minutes at Le Cellier - most of the other TS restaurants were around 1 hour).
May also be worth looking a the Dinner Shows (Hoop de Doo, Mickeys Backyard BBQ or Spirit of Aloha) which use up 2 TS credits but would have more than enough to keep the kids occupied.
Again as noted above, also consider the Character Meals e.g. Chef Mickeys, Crystal Palace, 1900 Park Fare, Asekrhus (these two with Disney Princesses), O'Hana Character Breakfast etc. These should definitely keep DD ocupied waiting for the characters or joining in with things. Incidentally, I have seen a few posts and websites with the tip that if booking a breakfast character meal, go for a later time rather than early as you may well find that the characters have more time to interact with the children, and you can treat your breakfast as brunch and not need any lunch that day.