Sci-fi/EOW - People fiend alien baby that smells of flowers and heals.

Hi, I'm looking for an end of the world/apocalypse book. I remember that there aren't many people left on earth, and lots of "bad guys", but I don't remember the apocalypse event. A women finds a farm with several men, and then a baby appears on their doorstep. They team up and leave the farm.

I think the baby's vomit or poop smelled of flowers like lilacs or violets. Later the baby heals people.

Later in the book they live in an underground base of some sort. Modeled after a video game?

And maybe this is another book, but I thought that in the end they go up on a space ship with Elvis and have to eat tons of noodles/top ramen.