Walk the Walk
Most children learn about Dr. King as an individual, but the changes that came about during the Civil Rights era of the 1950s and 1960s were the result of a massive social movement, not the actions of one man. A good way to press home that point with kids is to "just take it to the streets" as a group of family and friends. Plan a walk to raise money for a local charity or nonprofit organization that your children care about. Ask relatives and neighbors to sponsor your family for a certain amount of money per mile (or block). Although the cause may be different than those Dr. King fought for, the message to children will be the same: "When we all march together, we can change things."
School-aged children will enjoy helping to identify a worthy cause; they can also chart your trek on a local map. Make sure the distance you choose is realistic for younger children, but also long enough so they appreciate that old saying of the Civil Rights era: "My feets is tired but my soul is rested." Finally, when it's time to send in your donation, make sure you note that it is made in honor of King's memory.
Visit Another House of Worship
Many children think Dr. King was a physician; they have no idea that he was a minister who preached regularly. Celebrate his birthday weekend and promote religious tolerance by taking children to a church, temple, or synagogue other than your own. If you're Roman Catholic, visit a Baptist Church so your children can hear a gospel choir like the one at Ebenezer Baptist Church in Atlanta, where both Dr. King and his father preached. If you're Methodist, attend Saturday morning Shabbat services at a local synagogue. Share your thoughts and feelings with kids about the unfamiliar prayers and rituals, while promoting the common threads: "Even though we sing different hymns, we all believe in the same God."