It wouldn't ruin our cruise to eat at the buffet one evening, but our family dinners in the MDR are always a highlight of our cruises. It's a special time for us to wind down, chat, and be pampered with the full service. That's just us though. Everyone is different.
My wife's parents and our son (15) will be on this cruise. He hasn't been to Nassau before, otherwise I'd consider just staying and enjoying the ship.
We'll also be visiting in December with the same group plus our two college age daughters (who also haven't visited Nassau before). Hopefully we find something worthwhile to do.
Dan