They'll probably love public transit. When my DD was about that age I used to take the bus to work and would get off about a half mile early to pick her up at daycare. It was easier and faster to walk home from there, but she ALWAYS asked if we could take the "city bus" (not to be confused with the less sexy school bus, which she also liked but it wasn't quite so grown up and cool) instead. And nothing thrills my kids more than taking the light rail or Metro to get someplace!

Sarah