My ex is getting married, and the kids told me they are missing school. I was never asked, what to do?

My ex is getting married soon and my kids told me that he says they have to miss a day of school. I do not agree with this, and he has not even asked me if this is OK. He is suppose to return the kids Sunday nights, so this goes beyond his time. Our kids tend to get sick easily and miss school 9-10 days a year (sometimes more), so I prefer that they do not miss school. He and his fiance chose a Sunday wedding, but I do not see why this needs to impact school.