Are your tomato, squash and pepper plants dead or just looking really terrible? If they have healthy growth on top with some dead leaves at the bottom, they should be fine with care. It’s good to remove the bottom leaves anyway, as they’re most vulnerable to disease.
Summer squash are so prolific they probably won’t disappoint if you start them now. Same with tomatoes. Check the "days to harvest" number and count back from when nighttime temps hit 50 in your area. Then you can be sure to buy tomato varieties that will ripen in time. If you put in transplants, you can shave some time off the days to harvest number.
But don’t knock yourself out trying to grow enough to keep you canning all through October. A downsized garden seems like a good idea, with a new baby, and concentrating on a good fall crop of cool weather plants is a great one.