Something simple & pretty easy that the boys & I enjoy..is to watch the birds.
We found this incredible bird feeder at Lowes, but you can get a pretty basic bird feeder at Walmart for a few dollars. While you are there...buy some bird seed. Hang it up somewhere where you can watch the birds come to eat. We have it right outside of our front window...hanging from the trees. We love to watch the birds that come to eat from our bird feeder. It sparks some great conversation about different birds.