This is a great time for all ages. I went once with my boyfriend, and we came back with his grandparents. It's also a favorite class trip. (I know because my office overlooks the canal.) The boat is mule-drawn up and back on the canal, through one lock. Meanwhile, park rangers in period costume tell how the canal was built, how the locks work, and why it is a park today. On the trip back, they entertain you with period instruments, depending on the narrator's talent. On the two occasions, I was serenaded with a banjo and flute, and even taught to play the spoons! The rangers are great with children's questions, and they have their history down, too. Since the boat is covered, this ended up being a fine rainy-day activity by the way.
Runs April to October, Wednesday, Thursday, Friday at 11am and 3pm, Saturday and Sunday at 11am, 1:30pm, and 3pm. Prices are $8 adults, $6 seniors, and $5 children. See http://www.nps.gov/choh.