The topic of a «child-free» wedding is a hot-button one. Some think that weddings are supposed to be for families and that excluding children from your festivities is a slight to all the parents you’re inviting. Some think that all weddings should be child-free weddings since children tend to hate events when they’re supposed to be quiet, wear stifling clothes, and not scream at the top of their lungs. But most (reasonable) people tend to hold the opinion that whatever the happy couple says, goes. If they want things a certain way, then so be it. It’s their day, after all. Not yours.
Not everyone, though, is comfortable with that level of lack of control. Some people tend to think that the world revolves around them and their whims and that they’re an exception to any rule that has been laid out. You tend to want to avoid inviting these kinds of people to your wedding.