Even the lawn of your manufactured home is nature, and being in the backyard should open the kids' eyes to the wilderness around them. Start the night off with a nature hike around the neighborhood. Take some binoculars to spot birds, and collect different leaves or plants. At home, ask the kids to try to identify the birds or plants they saw from a field guide.
But nature isn't about just knowing what you're looking at; it's also about looking, period. Give the kids a disposable camera and ask them to take some pictures of the natural world in the backyard or neighborhood, and create a budding wildlife photographer.
Bonus lesson: Take the opportunity to teach the kids about how tribes native to the area lived before settlers moved in. See if you can find some things they gathered to eat or try to make some tools they used.