Here's a great outdoor activity - a NUMBER HUNT! Stick foam numbers (or simply write) onto plastic garden label sticks. Hide the sticks in the garden and then send the kids outdoors to find them. Once found, ask them to line up the sticks in the correct order.
sorting rocks-light-medium-heavy and orange, white, gray and brown. Extend with: comparisons: bigger than, heavier than, musch smaller than and use the > < symbols to compare while weighing or balancing
Blackboard paint tree slices for natural mark making on the go. Great outdoor mark making idea. Kiddies could do this before working in their sketchbook. A basket of these for children to take out and explore.