Congrats on your 30 years together!
Not a cruise crazed expert, I just try to help out when I can.
Since this is important, I would not wait until your first seating. The table assignment will be on your Sail & Sign Card. I would go to the dining room and check out the assignment immediately. If it is not right, find the Maitre'D ASAP. If you wait you will be further down the list of others wanting to change.
I hope it is right for you from the start, and best wishes for a wonderful anniversary cruise