We would go on nature walks all the time as kids. Here's the idea-simple-doable. Take children on a walk, around the neighborhood, at a park, whatever and have them search for several leaves. When they've picked out the leaves they think are their favorite bring them home. Place a single leaf down at a time or do several together in a group on a table. Place plain white paper on top of the leaf/leaves and rub with the side of a crayon over the entire piece of paper. They'll get a rubbing of their leaves and keep it for as long as they'd like. Use different colors of crayons over each leaf for a cool collage type picture. Picking up leaves of different varieties of trees makes for an interesting picture too. Have the child research to see what leave goes with what tree and write it on the picture. This activity encompasses physical activity, respect for the earth, biology and art. I love multi-level activities.