In most cultures there is usually at least one child in the entourage - the flower girl. Mainly though, weddings are an adult affair. It can be quite boring for kids.

Imagine if you're four, dressed in formal clothes then told to sit still for at least an hour while the ceremony goes on. Then when you get to the reception you still can't play and aren't allowed to touch the beautiful cake. What a bummer!

As the hosts, it is up to the bride and groom to decide whether or not the kids are allowed to be present. Keep in mind that when bored, it is perfectly normal for kids to run around, screaming at the top of their lungs. Their parents may or may not even be able to keep them in line.

You can actually specify it in the invitation. Most parents will quite understand of the fact that the event is not very comfortable for children; in fact they will usually think of it themselves. It will still be better if you explain it to them in person rather than as a note on the invitation.

On the other hand, if you don't mind their presence, it would be greatly appreciated by the parents of the kids if you would include them in your guest list. If there are a sufficient number of young guests, you could put them together at one table so that they can interact with each other and keep each other amused. Who knows, you may actually be introducing future mates.