Learning about and respecting nature is something that is very important to our family. We took a trip as a family to a local nature perserve a couple of weeks ago. With us, we took magnifying glasses and bug catchers to see what we could find in the long grass and "forests". The kids had a great time following daddy along the grassy paths. We used our magnifying glasses (bought from the Dollar Store) to look at the flowers beside the path, being sure not to touch or pick any of them. We saw really neat things INSIDE the flowers. It was a great learning experience for both of them. Once we finished our hike we sat down and ate a picnic lunch together which was the best part of all!
Don't think that there are not nature preserves close to you. Ask around. Check the internet. I'm not talking about National Parks, these are just areas of land that are meant for the public to hike, ski, walk and enjoy nature. I didn't even know about this area and I have lived in the city for 11 years - in the area for 28! So do your research - I bet you will find something close by!