What to do in the event of an "explosion" at my brother's wedding this July?

OK so….My brother and his best friend are having a double wedding this July. They’ve known each other since they were about 8, and they’ve known the brides (sisters) for 6+ years. My brother and his fiancé have been engaged for 4 years, the other couple for about 3 months. My mom and the bride’s mom have known each other ever since my brother met his fiancé. Now that the wedding is finally here, though, they’ve had quite a few heated “discussions”, and there have probably been some that I don’t know about. And my mom kind of…“explodes” every so often (twice a month about), and especially on stressful days, like Easter, Thanksgiving, and Christmas (I can’t remember a holiday that she didn’t). I would be very surprised if she didn’t at the wedding. So what should I do? I usually walk away, but that might not work…
I’m having nightmares that she ruins the wedding and various outcomes happen.