Using the kid city:
To prepare you could draw out an outline of the city ( Little squares to show where buildings would go, and possibly roads.), also you can cut up cardboard as pre-made "walls" for the buildings. I would introduce how the you use steam to plan a city, talk about how people like engineers and city planners need to think about what you need to survive and thrive in a city. Then go into how they are going to be the engineers of the city. Have them name different places they want in the city, and vote on where it should go. You can check for understanding by asking them why that building is important, and ask what they need to make that building. You can make sure learners are engaged by giving them more buildings to make. You might encounter that kids lose interest. Also might worry that kids will fight over what goes where and who gets to draw. You can then wrap up the lesson by having the kids share what they built and why, asking why a city might need this is a good idea.
Teacher Slideshow:
https://docs.google.com/presentation/d/1ExKAwF883BUMA6VeoCJ0bGpxG8FeBbqJt9lIW89DGiA/edit?usp=sharing