Debbie,
I like the Venn Diagram idea. Since this is kindergarten, did you put pictures for them to refer back to? Or did you just fill out the words? I also like the idea of watching a facts and fun video on Discovery Streaming. I hear they have great resources there!
When reading over your thoughts I also wonder if having visuals for the students to go back to. You could also try playing "president" online with sites like: PBS http://pbskids.org/democracy/be-president/ or Scholastic http://www.scholastic.com/kids/president/.
Venn diagrams are always fun, and and a great way to visualize similiarities and differences.
Would the students benefit from, perhaps, inviting the principal into the class in order to get his/her take on what they came up with?
I was going to watch the video, but I don't have a Discovery Account. I think the children liked having the video to watch, it seems like so many relate when watching on TV!
I also like the idea a peer had of inviting in the principal to check out what your class came up with on the diagram.