A sustainable vegetable garden means one that can be sustained over time, and would necessarily involve I) growing food you want to eat, so you are motivated to continue growing, II) growing economically, so that it is worthwhile doing, as well as III) taking care of environmental issues, so that the ground will continue to support growing.
I) The plants to be grown should be chosen primarily on what your family wants to eat, and what will grow in your locale. After that, Consider using heirloom seed rather than hybrid, if you are very concerned about losing the ability to replace seed each year from commercial sources. However, growing and saving your own seed is difficult and time consuming. An excellent answer to this dilemma is the Garden In A Can heirloom seed provided by Mountain Valley Seed Company (www.mvseeds.com). Other seed companies may have something similar. I recommend you buy a can of this triple-sealed seed, store it against the possible disaster, and then buy and use the best seed you can get and don't worry about trying to grow for and save your own seeds.
II) Using the best growing practices, such as those taught by the world-renowned Dr. J. R. Mittleider, (see http://www.growfood.com)assure you the greatest yield of healthy vegetables from the least space, and with the least amount of labor and financial inputs per unit of production. A family can be self sufficient in their food requirements from proper gardening of just a small fraction of an acre, and this is the greatest evidence of success in achieving a sustainable garden.
III) Gardening should always be done without injuring the land, but rather should improve the land, so that it will continue to support healthy plants indefinitely. Therefore, pesticides and herbicides should be used very judiciously, and wherever possible these issues should be handled by cultural practices as taught by Dr. Mittleider such as 1) eliminating all weeds from the garden area, 2) watering only the plants' root zone, 3) beginning plants in a protected environment for a fast, healthy and strong start, 4) feeding plants proper amounts of balanced natural mineral nutrients to assure fast and healthy growth, 5) harvesting all plants at maturity to avoid allowing pests and diseases to multiply, and 6) discarding any bug or disease infested plant parts away from the garden, and incorporating healthy plant parts into the soil to improve soil structure.