This may not work for picky or budget-conscious people, but we ate at Tiffin's for Thanksgiving 2021. They had a special turkey meal. I think it included app, main, and dessert for prix fixe. They also had their regular menu, which is what we got, because none of us like turkey that much. The Thanksgiving meal sounded really good and was tempting, even though I don't like turkey. It was great for our son, because he will eat steak. They always have meat, fish, and a vegan option.
Another option, might be Rainforest Cafe. I know the food isn't the best. I also don't know if they do a special Thanksgiving option. However, they have a massive menu that appeals to most people. They have the 2 locations, AK and Disney Springs, which are accessible without entering a park. They also have fun big desserts that people can share.
LTT is probably not a good option for the pescetarian, unless they are willing to just eat sides. The only other option there right now, besides the turkey dinner, is a vegan option. It personally looked kind of gross to me, and I have been vegetarian before. Diamond Horseshoe might be the same exact menu. EDIT: On second thought, the vegan option looks better than I remembered but still not amazing. No fish option.
There is also Cinderella's Royal Table. It's not amazing, but our meal was good. They have scallops which were pretty decent.
I think something like Whispering Canyon could work. You could even do breakfast. The veggie option breakfast there was really good. It's served family style, but the veggies/allergies get their own skillets. You could still share things if you want. I don't know if they do a special Thanksgiving meal, but it seems like the kind of place that would. They have a chicken/vegan sausage/salmon skillet. I bet they could remove the chicken. They were fine with customizing the skillets to some extent. They also have entrees, one of which is salmon.
Also, what about Jiko, Sanaa, or Ale & Compass? I know all of those are good and have meat and fish options. Maybe not specials for Thanksgiving at Jiko or Sanaa though.
I would suggest doing a google search to see if these places have had a Thanksgiving meal in the past. It's probably a good indication of future behavior.
Good luck!