Here are some helpful links I found. Pretty basic, but a start:
Sand ceremony: How to Use a Unity Sand Ceremony for Blended Families | eHow.com
Kids part of ceremony: How to Incorporate Children Into a Wedding Ceremony | eHow.com
Kids and planning: How to Incorporate Step Children Into a Wedding Ceremony | eHow.com
in vows: How to Incorporate Stepchildren Into Your Wedding Vows | eHow.com