Cutting & Bottling Honey

Knott's Berry Farm sold phosphorescent paint. Pretty much all watches had "radium dials". There were lots of dangerous chemicals around in those days (40s and 50s).

Pretty much everything in the Gilbert Atomic Energy lab kit you can still get from educational suppliers today, is not something particularly dangerous, and can be an entertaining component to actually teaching modern physics.

From what I've seen before, it basically had four radiation detectors: Geiger-Muller tube counter (which unfortunately is and was kind of expensive, leading to cheaper kits with everything else), an electroscope, which is something you can build from household items, a phosphor based detector, and a cloud chamber. A cloud chamber lets you see paths of ionizing radiation and building one was one of the more fond memories I had from middle school. The kit also had a selection of small radioactive sources , something else still available from educational supplies (price has gone up a lot in the couple decades since I last bought some). These are not particularly dangerous as long as they are kept outside of the body, like a lot of things in our day-to-day life.

And for that matter, elemental and many other forms of mercury have virtually no evidence linking it to causing cancer in humans, with some evidence in animals for methymercury. It is still a very dangerous substance without care and not something I would give to a kid, but it is not dangerous because it causes cancer.

I managed to survive mercury, radium watches, and chemistry sets, and now look at videos of kids setting themselves on fire because they have no appreciation of dangerous activities. http://www.click2houston.com/news/crosby-boy-14-sets-self-on-fire-playing-fire-challenge-game/27237628