Here are some links that might help if you decide to share the meaning of this day with your kids:
If your kids are not ready to understand, get out and volunteer. Do something to help your community. It doesn't have to be anything official, just something...anything.
I will be using the above resources to help me explain the day to H, and then after J's nap, we'll all be heading out to pick up some trash littering our neighborhood. If there's anything I've learned from Dr. King, it's that we can all make our world a better place, one tiny step at a time.
