Keep their hands busy. Children of all ages like to touch. If all they can find is the crystal vases you used as centerpieces that is what they will use to entertain themselves. Provide crayons, art supplies, coloring books and some party favor style toys to help keep them entertained. With this in mind, if you are having an abundance of very young children you may want to skip the candles and other hazardous items in your décor. Children are curious and it is better to prevent disaster if you can. Consider led candles and other alternatives.
Hire a babysitter. Hiring one or two people to help keep an eye on the youngest guests at your reception can be a great idea. It is, after all, a party so parents may be a little distracted. A few people to help entertain and keep an eye on the entrances will be a welcome gift to your guests. Just a couple people to help with art projects or other activities will be enough. Ask your local friends if they have reliable babysitters that would be interested in a few hours work and a free meal.
Have a special dance. Set aside a time for your DJ or band to play a few games with the children. Musical chairs, the hokey pokey and limbo are a few fun choices. This will make children feel like they are in the spotlight for a little bit and make for some great photo opportunities for your albums. Have little trophies or prizes for all the children to make the dance even more fun.
No matter what you decide about having children at your wedding stick to it. If guests complain about your decision have simple response ready for them. Say something like “we want a worry free day for all the adults. We really hope you can find a babysitter but if not we understand” or something like “we want to include everyone in our celebration even our youngest friends and family”. In the end the wedding is yours and so is the decision.