I would read a book about shapes first as part of the discussion on shapes. I like in the end when the students come back and tally their results. You could also do a bar graph with the tally marks.
We live in a world of shapes. That window in the living room is also a square, that steaming bowl of chili is a circle, and the bed your son regularly refuses to sleep in at night is a rectangle. Learning to identify and categorize different geometric shapes is a big goal for early learners