Have a day where you only use public transportation for an adventure.

“When I was pretty young, maybe 6 or so, my Dad and I were headed into San Francisco for a baseball game. When we got there, the game was cancelled due to rain so my Dad was left scrambling for something to do after a long trip into the city. He landed on a "Public Transit" adventure much like yours, and we spent the day riding every form of transport he could think of. In a city like SF (and Seattle!) that means a pretty wide variety of interesting vehicles. Everything from a bog standard city cab (whose rather odd smell I can still remember) to cable cars, trolleys, ferries and the absolutely magical bendy bus. All these years later I still very fondly remember that day, and I'm sure your little guy will too. Way better than any stupid baseball game. ;)”