My daughter is a collector of all things in Nature. Where ever we go, she has to pick up some 'treasure'. Whether it be a rock, a dead leaf, a stick, a feather, a flower, pulling a few leaves off a plant, or what ever catches her eye. She finds value in even the most ordinary of things. She doesn't like to throw it away. But ever week we dump it all outside and she gets to refill her bin with new treasures. It has a lid that snaps on and off very easily for little hands. The lid allows her to set it next to her where ever she goes and even take it to bed with her.
I read something like this somewhere in a book and I can't remember where, but I loved it. This is me paraphrasing it:)
Children are very imaginative. A simple bowl of water, a few toys that float, and maybe some measuring cups can keep a kid entertained for hours. Give them a few ideas of how to start and sit back and watch them get to work. You will be amazed at what they come up with. A sibling and or friend helps things get off quickly and tends to keep them focused longer. Leaving you time to watching the magic happen:)