If the timing is right, I would bring a mushroom grow bag with mushrooms sprouting.
If not… probably my radiacode gamma spectrometer and some of my radioactive items. Maybe a clock with radium painted dials and a piece of trinitite. I think that there are many different points of discussion that can be of interest to a broad audience (radioactivity, spectroscopy, electronics, US labor law story of the radium girls, nuclear explosions, background radiation… etc). As a bonus I can bring a UV flash light and show the radium fluorescence. Adults love UV flash lights.
Amazing work! Thanks a lot!! Took me a few days to get to it but I have upgraded now and it looks great 😄