Let's face it: only Cruella De'Ville can completely abolish children at a wedding. (and who would invite HER??)
Your next question is: How to provide some form of entertainment during the reception and cocktail hour for children?
If your budget is unlimited you can of course, hire a Circus complete with acrobats and elephants. Okay, that's off the chart for most of us. Reality check. If your wedding is outdoors and there is space, consider croquet or plastic horse shoes or bean bags such as the Toss Across game. Chalk and cement are easily washed clean afterwards if the venue permits. When you have a general idea how many children you can expect to attend your celebration then you can start focusing on how to entertain them. Consider their ages and the time of year and venue. Even if your event is indoors if there is space such as a back yard or park area associated with the venue you might consider hiring someone (with criminal background check!!) to entertain the children outdoors such as a balloon modeler. For indoor and winter events look for a storyteller, someone who comes to your event and entertains the children with a story using finger puppets etc. They may stay an hour or longer depending on the individual. Be sure to ask for background checks on anyone hired to entertain children.
Paper dolls are a great way to entertain children old enough to handle blunt scissors. You can have the dolls already cut out (if you want to avoid scissors) and in little bags or packages at each child's place. They could even double as the children's table place cards. Crayons and coloring pages are another indoor entertainment to consider. Blank sheets of construction paper allow children to draw and create their own images. Whatever you plan for children be sure it is age appropriate. Also remember they will be wearing party clothes so vigorous sports might tear or dirty their clothes. Read more about planning for children at your wedding at wedaholic. Vintage Paper Doll images can be found here at the graphics fairy blog.