PILGRIMAGE by Tom Abrahams.
Here is the description from Amazon:
PILGRIMAGE is a stand-alone post-apocalyptic story of survival. It was previously published as three separate novellas: Crossing, Refuge, and Advent.
High School teacher James Rockwell is vacationing in Maine with his family, when an earth-changing explosion sends them on a race for their lives. Their first step is escaping an island in the midst of a tsunami, and it only gets more dangerous from there.
Can they find their way home as civilization crumbles around them? And if they do, what horrors will they find?
--I really liked it. The protagonist was not a super-duper-great-at-everything-hero and the survival aspects were excellent. Recommended.