MI - in the park or further afield - collect as many leaves as you can, identify them when you get home, and then do "leaf rubbing." Or stick sycamore "keys" on your noses and pretend to be unicorns. Make "fish bones" from horse chestnut leaves.
Treasure hunt - when we lived in UK, I did this for a group of 6-8 year olds around our village - eg what is the name of the house with the wagon wheel outside? On the war memorial, who died the furthest away (bizarrely it was someone in USA), etc etc. You can also do collecting things - a feather, an interesting stone, two different leaves, so can adapt it for different ages. I also did a larger scale one as a fundraiser for the scout hut.
In the garden - planting seeds (nasturtiums are good), plant them in a pattern, water them and watch them flower (not all on the same afternoon, obviously).
Old fashioned games - "French Skipping", Port and Starboard, pompom etc etc