Children create a family-friendly atmosphere and allow the couple to include their own children or favorite nieces or nephews.
If you have your own children they can be included in the wedding ceremony by asking them for a simple affirmation. The stepparent can offer a token. A bracelet, a locket or watch can help the child feel special.
Note, too, that children can bring a wonderful element of "surprise" to a wedding ceremony! If they are included the couple must be accepting of their special needs and behaviors.