All she wanted to do when given complete freedom of choice was to "go on the train, have a milkshake and watch the other trains going". So that's exactly what we did. We go one stop, sit in the station cafe and watch the trains coming and going until she's finished her milkshake. She then decides which train she wants to get on to go home. This is definitely her favourite way to pass a morning and we'll be doing it again this week.