The obstacle course sounds like an exciting idea to keep the kids entertained! Nature provides so many interesting features to explore; it's like a free outdoor playground!
An adventure challenge like that can be a great way to tire the kids out too, haha! A good old-fashioned game with a twist seems more fun than the usual running around in circles. The Rainbows & Pots of Gold activity sounds like a perfect arts and crafts addition back at the campsite; I'm sure the little ones would love the creativity involved.