Some trains operate at other times of the year as well.
To get there, take I-35 Exit 111 at Ames. Go west on U.S. 30 about 14 miles to Boone. Call to confirm the schedule and make reservations. Children younger than 3 are admitted free if held, but on the train I rode, there would have been plenty of space for a kid to sit. The trip takes about 1 hour and 45 minutes.