Right after listening to 9 of Mark Goodwin’s audiobooks which are also apocalyptic, this story line is weak and is hard to imagine. Quick examples:
One character named George takes on 4 trained, armed soldiers and incapacitates each of them, saving the day and the heroes of the book.
Next quick example: a boat that is big enough not to capsize when an adult runs and jumps into it (a flying leap) requires only a single gallon of gasoline to go a long way immediately following a short time of full throttle while carrying 5 adults to escape risk from gunfire from the shore. Any boat owner would know that a gallon of gas would be consumed very quickly in a vessel which would be able to do these things.
Not well thought through, and could use some pretty basic editing to maintain consistency in the story line. Recommend Mark Goodwin’s audio books which, while not perfect, are basically believable, at least.