Giving you a bump here as we've never been in the restaurant during fireworks but people on these boards have reported that you can indeed see them from some tables. Perhaps if you ask for such a table when you checkin and indicate that you'd be willing to wait you might have luck.
When we were there last april for our anniversary, we requested a window seat, they said it would be an additional 45 minute wait so i said that would be fine. Well about 15 minutes we were seated at the best window seat in the castle (in my opinion anyway). We watched the fireworks and it was great, they dimmed the lights, so you could see better, very romantic.
You can definitely see the fireworks from the inside of Cindy's Castle. We ate there last summer and timed it so we would still be in the castle during the show. It was beautiful. They dim the lights so almost anywhere in the castle you can see the fireworks. I would definitely hold out for a window(or close) table!
What time for a early July reservation after the fourth ,would be a good target time for for dinner to see the fireworks, My 60 day window is approaching to make PS arrangements.