Hi
People, or at least British adults, certainly British southern adults, are in my experience very reluctant to start conversations when you don't know if the other person wants to talk to you. In my experience it also takes some time to get to that point.
Layout is probably important, make people share space with a small group of strangers.
Were any of your activities designed to encourage people to interact with each other and start talking? An option might be to create an activity where you have to communicate with our neighbours to make it work. Cambridge Science Centre used to do chain reactions (Rube Goldberg machines - not sure if they still do) which would cause people to communicate with the links on either side to make it work. You may want something that causes more interaction than that...
It may possibly be better to get people to work in groups they didn't arrive in on some project. Though that is difficult with families. Though it is difficult to find projects which are open ended enough but won't appear fatuous, particularly if people are just turning up off the street. Are there any historical jobs one could reenact? Or just Assemble parts of something really big that people can put their stamp on and what their neighbours do affects them.