Its possible but not likely.... maybe and that's a very thin maybe - soup or side salad, but not a appetizer to replace the dessert. In the past... way in the past... possibly, but now I really don't think it will work out. Maybe just budget to pay oop for appetizer or side salad, and with you sharing 1 TS, I really don't think that they will let you. When sharing a TS you might want to look at the menu and go from there before you make your ADR's.
I have some friends and when at the world they share for every meal. She said that at Teppan Edo is easy sharing with enough food, and they did let them substitute dessert for a extra salad, but this was well over a year ago. At LTT at lunch time( it family style in the evening so that will not be an option) their favorite splits are the Pilgrims feast and have also split the Grilled chicken and pasta, and at Tony's spaghetti. She did tell me that she felt when dinning in the resorts they are more accommodating when splitting meals, they normally do TS for a late lunch. They both have some health issues and grazing method works for both of them, and this is how they eat in their daily life.