I love vegetable stew with lots of root crops and they taste even better out of the garden. Radishes are another root crop that grows well in the fall. They can be started late - only 7 weeks before your first frost. They're a pretty easy vegetable to grow, so they're great for the kids to tend. As an added bonus, they germinate quickly, so you have some immediate positive feedback.
Carrots taste sweeter in the fall.
Plant them 13 weeks before the first frost and wait until after a good hard frost to harvest them. Last year I left my carrots in the garden over the winter and they were fine. It's an easy storage method. In really cold climates you might have to mulch them. Turnips only need to be started 6 to 8 weeks before the first fall freeze.