If you're not out there weeding and planting and tending this time of year, you won't have a nice fall/winter crop to harvest. You don't need a fancy greenhouse either, just some row-covers if you plant cold-hardy crops. If you want to go the fancy greenhouse route, check out Eliot Coleman's books to learn more.
Here are the kids, weeding (before harvesting tomatoes and peppers); no, they don't always have goofy grins while weeding, but they don't complain about having to do it either:
Another nice fall crop is kale. It's highly cold tolerant. Hubby grew 2 different varieties this year:
"I may not have gone where I intended to go, but I think I have ended up where I needed to be." ~ Douglas Adams