The London Museum of Water and Steam
This is my pick for the best place on my entire Steam Tour to take your littlest Steampunks. There are fun, hands-on exhibits about the water cycle and great info about the history of harnessing the Thames and combatting the Cholera outbreaks through London’s history. But the most exciting parts of the museum complex is room after room of real, working steam engines. They don’t run every engine every day, but I was lucky enough to visit on a bank holiday when they did run every engine for at least 15 minutes at some point during their open hours.
In the courtyard there are some smaller engines as well as a station to make giant bubbles in the afternoon, so that is another plus for kids. There is also a replica of a Victorian-era workshop where all the machines run on the same belt system (the original workshop was destroyed during the Blitz) and they offer tours.