Grownups like hands-on science too. At science festivals and museums we usually hover at the back, letting the kids have a go. So if you include experiments and demonstrations in an event aimed at adults, you might find that people love it – or even find it moving if they didn’t get a chance to find out how interesting science was as a child.
Here are some sources of hands-on science you can do safely outside of a lab setting. But watch out, grownups are almost universally worse at listening and following instructions as kids…
Messy Church Does Science – hugely popular, and easily adapted for adults
The Naked Scientists – where I learned how to make my hugely popular hoover bazooka and some other great demos
Cool Science Tricks: 50 Fantastic feats for kids of all ages
And there are plenty more online!