You should wash it as directed when you first take it out of the box to remove any grime or oils from manufacture. After you season the pan, it should never come within 6 feet of soap for the rest of your life.
I clean cast iron with hot tap water and a stiff brush, then wipe out with a towel (to avoid rust). Best to let the pan cool from the stove before doing that. Easier on the metal, and no big clouds of steam to burn you and set off the smoke detector.
Make sure you will the dutch oven to your kids.