The main thing would be to have a functioning society by the next generation, so that they don't just sink into a dark age lasting thousands of years. If they could make a steam engine, they can settle at the 1800 technology level, and maybe make a reasonably quick comeback in a couple hundred years. But as they are heading in the show, they are fighting each other and heading back to the stone age.
If I was going to move the group, it would be to Chesapeake Bay, so that I could take over a marina and make a living from the ocean. You could spread out settlements all along the coast using boats, and rebuild the country more easily.
But if I stayed inland, I'd still go with the canals before I tried to build a steam engine. They are super low tech, and even with the low population of Alexandria, the Kingdom, and Hilltop, they could get built. You really only need digging tools, wood, rope, and horses and you're in business. Rivers are fine, if you only want to go down hill. Going up hill before steam power was really difficult. And that's another reason why I think it would be fun to see the show do these things. The problems and solutions are real, and they've been encountered before. It would be like watching the second colonization of the New World.
If I’d had my way, Carl would’ve turned and popped up as a walker right in front of Rick and Michonne.
Now *that* is pathos.
:)