I don't think that the Plaza is a good choice for a TS credit, but love the place. Their lunch and dinner menu are the same, mostly sandwiches. There is a nice variety to the lunch menu at LTT and it's not a character meal, nor buffet. But I would suggest if you want dinner, why not hop the resort monorail and zip over to the Concourse at the Contemporary or Kona Cafe at the Poly, of the GF Cafe at the GF and have a nice early dinner and when you're done, grab the resort monorail and go back to MK. The family gets a nice treat of riding the monorail, it's barely 10 minutes away, and you're get a better meal in a more relaxing setting.
BTW--I noticed your trip is December, but visiting the other resorts, you'll also get to see how they are decorated for the holidays...