To early - I would move to later if possible to see the show there or earlier to find a place on the lagoon to watch.
When we were there last year this very large party who had eaten when we were seated, was continuing to sit. The server asked if there was something else that was need, they said no just waiting for the fire works. It was 8:00.
I understand wanting a good seat, but not a the expense of someone else. I'm sure that there were other families waiting for the seating, and of course the server who could not move tables, being a past server it is important to move your table. When I worked the number of tables you waited on in a night was kept, If you did not fall into the average of the company wanted you to wait on you could be written up either way. I'm sure that with a volume as high as the restaurants at Disney this is something that they do take a look at.