It is interesting to me how we can all sense a tense interaction. Some people do not make it hard to guess at, but those who are less overt in their distress still give off a tangible vibe.
As an experienced wedding planner, I wish I had a professional mediator or a magic wand to help my couple’s special day be completely drama-free. As those offerings are not a reality nor practical, I recommend planning ahead in the following ways:
Most of us know which members of our family and social circle are more likely to cause issues. Proactively setting boundaries within yourself and then verbally to those people can take fuel out of future fires. If someone is determined to cause trouble, assign someone you and these members trust as the buffer or mediator. Even more controversial, formally uninvite them to be a part of the planning and event. We choose who gets to be an active participant in our lives and deserve to have the peace that comes when our concerns are addressed ahead of time.
We are the stewards of our time and energy. Plan to be well rested and to have any other obligations satisfied before meeting new family members or before any pre-wedding gathering. These relationships are like any other valuable ones we might nurture, so the efforts are sometimes required to be great. Take inventory of yourself. You can proactively prepare and address many disruptions so that you can enjoy the reality of your wedding day, no matter what.