We didn't tell Little Man about the event, rather just explained we were going to a new train station. That was all he needed to hear. He insisted on wearing his Thomas the Train shirt and Metra hat. Sidenote, ask him who he is and the response is, without exception, a "train engineer."
The event was fun and crowded! We didn't stay long, but the impact was dellible! Gilbert loved it all. We even snuck onto a freight engine (the line for the official tour trains was too long!).