Most interesting outdoor activity for kids is a bike photo safari. This is where the parents and children jump onto their bicycles accompanied with a camera of course and plan an interesting route which they hardly use to commute to anywhere and go discover its beautiful secrets by collecting pictures and videos of interesting happenings or eye catching scenarios.
I do recall when I was in per-school we had a couple of outdoor games like one called potato spoon race where we used a spoon with a potato on top of the spoon and race with each other making sure that the potato doesn’t fall off while running towards the finish line. We still this other one where you fit in a sack, waist high, hold it with both your hands on the side and hop to the finish line making sure you don’t fall or your opponent gets to the finish line before you do. The other one which still remains interesting is the three legged race where you tie your foot to your partners foot so that both your feet be as one and the other two remain free that’s why the name three legged race name comes from. In this game children like to pair with adults so if you do that just keep in mind children take smaller steps so be on the lookout for a tripping hazard.