I don't want to disappoint you but you probably will not have a great view of the fireworks. the windows are not very big up there at all and only a couple of tables sit next to the windows.
With that I still would take the 925pm dinner esp since you have lunch at LTT. We always go to dinner at the castle and have never been disappointed with the food or service. It's one of our favorite places to eat each trip. My DH and my dad love the prime rib. I usually get the special seafood dish and it's wonderful.
If you have not heard they have a new special dessert. It's like the Cinderalla Slipper served at the GF but it's bigger and mostly chocolate. I saw a pic of it and it looks awesome. I'm not sure if you have to special order it or not through. At the GF you have to special order the dessert 24 hours ahead but I'm not sure about this new dessert.