The Outdoor Science Lab for Kids: 52 Family-Friendly Experiments for the Yard, Garden, Playground, and Park is a good guide to home science experiments for kids, usually with adult involvement, ranging across a fairly wide range of age but mainly, I'd say, middle school for unsupervised work, or pretty much any age if supervised.
All of the experiments can be done by adults with younger kids watching or being involved to varying degrees.
Most of he experiments cost little or nothing, depending on where you live (like, do you live near a pond?) and what the phrase "common household…