Another fun thing you can do,…
Another fun thing you can do, when searching for shells on the beach, or stones in a river, is have a pocket full of pre-collected or bought gemstones/shells in your pocket and silently disperse them for the kids to discover treasure.
It would be best if what you leave behind fits the geology of the area. You can intersperse some lessons about time/evolution/sediments/fossils, etc.