Constitution Day is coming up. Here is what I usually do to teach my students about the Preamble. Feel free to comment and post your own ideas to this thread.
I use the book We the Kids by David Catrow.
The objective of the lesson is to understand the preamble and to paraphrase it and put it into visual form. In my kindergarten class, we did this as a shared writing activity and the students drew pictures to represent the different parts of the preamble.
For more specific instructions for the lesson and for different directions for creating a Preamble quilt go to Preamble Lesson.