Discuss it Beforehand
Reach out to your ex, before the wedding, and handle any drama or unresolved issues. (Now remember, before the wedding doesn’t mean the day of the wedding – we’re talking about more like a week or so before the big day.) Agree on a location that is neutral for both parties and doesn’t bring up any bad memories. Be honest and disclose your feelings with your ex. Explain why you may feel uncomfortable and the measures that could be taken to prevent any bad feelings.
Keep in mind, odds are this is not the last time you will encounter your spouse at an event. The two of you don’t have to be best friends but having a civil understanding will help alleviate any issues in the future and will allow you to be more comfortable with the situation at hand.