The story begins even before the title page of this warmly satisfying book, capturing a family’s unabashed eagerness to get their short but precious summer beach vacation started. We see the five of them, plus dog, outside their suburban home loading up a minivan with all kinds of beach paraphernalia, then arriving at a blissfully isolated summer house, where unpacking — frustratingly — has to come before that first run down to the sand. Caswell’s peppy rhyming text is aimed at the youngest beach-lovers, with lots of lists. (“Marco Polo. Dives and dunks. Body surfing. Floating trunks.”) Bates’s dreamy watercolor art seems to drench the pages in the soft yellows, golds and oranges of the sweetest weeks of the year.