When you're experiencing challenges with your in-laws, step back and take a long view of the struggles. Most kids benefit from as much love as they can get, even if it doesn't look and feel exactly the same between the parents and the grandparents. Speak up when you need to... but step back and let go when you can.
Whose wedding is this anyway? Yours? Yes! Your financé's? Yes. But many others lay claim to the event.Your own parents may see it as their graduation party. Your grandparents may see it as the culmination of their life's work. Your siblings may want to make you queen for a day or share the limelight.