How would you teach third-graders about the Church?

In two weeks' time I will be a catechist for third-graders at my parish, St. Hedwig's in Trenton.  The curriculum for the year (using the Sadlier series) is "We are the Church".  So I get to teach these third-graders about the Catholic Church: the who, the what, the how, the why.

On the first day, I'm going to ask them a few easy questions to get their brains working: what is the Church, who started it, who belongs to it?  But then I'm going to step back and ask them a more basic question: what does the word "church" mean?

How would you talk to the third-graders about the Church?  What language would you use (or avoid)?  What points of history and theology would you make (or pass over)?  And, most importantly, how would you relate it to them so that it's not a bunch of head-knowledge, but helps them grow as individual Catholics in that Church?