When you're planning your wedding, you think long and hard about who you want invited to that wedding. Most people understand that the wedding invitation is not necessarily extended to their loved ones. What a lot of people seem to have a hard time understanding is that their kids aren't always included in the invitation. While it would be nice if everyone could afford an on-site daycare for children present, the fact of the matter is that that is not a reality and children often times disrupt weddings. So how do you make it clear to your guests that their children are not invited to the wedding?
Traditionally, wedding invitations specifically request attendance by name. It's seen as rude to write something like 'No Children' on the invitations. A better idea is probably to spread the word among friends and family that the wedding will be one without children. Don't make exceptions for anyone. Offending guests who would have liked to have brought children isn't worth it.
If a guest brings uninvited children anyway, don't turn them away. Try your hardest to make the wedding a happy occasion and accommodate the children however you can.