Girl Scouts and "Plot"

Since I'm the resident writer in my hometown I volunteered to take one of my daughter's Girl Scout meetings to give the fifth graders a lesson on creative writing. The plan is to talk about writing, do a little writing, and then head to my husband's printing company for hands-on tour of how books are printed and bound. Fun, right? But in looking over the Girl Scout manual I discovered something interesting and it reminded me of all those years in grade school when my own teachers tried to drill this same concept into our pea brains--"the plot of a story is the beginning, middle and end."
If this statement were true the following would be a plot:
We left the house in our car. We drove to the grocery store and bought food. Then we drove home.
This has a beginning, middle, and an end. But who cares about someone going to buy food? This is simply a second-grader's ramblings, not a plot. Plot is the compelling element of the story that makes the reader keep reading. Plot is the why of the story. What do the characters want to accomplish?