The family consists of a middle aged married couple, "Father" (John Mills) and "Mother"(Dorothy McGuire), their two teenage sons, Fritz (James MacArthur) and Ernst (Tommy Kirk), and their precocious animal trapper little boy, Francis (Kevin Corcoran). The only thing preventing this kid from capturing tigers and elephants is his parents' permission. Which isn't realistic, sure, but it was funny and it's a Disney movie so I don't mind. You can be as unrealistic as you want so long as character motivations hold up. Unfortunately, they really don't.
The shipwreck is a pretty impressive full size ship. When Fritz suggests they put up a flag signalling distress, Father wisely remarks that anyone who sees the wrecked ship is bound to know they're in trouble. The movie stops to show Fritz's chagrin as Father smiles at his still unready son who's trying to be helpful. Meanwhile, 90% of everyone watching the movie is thinking, "Anyone passing will see a wrecked ship but a flag will communicate that there might be survivors."
Mother, who looks rather more late Victorian than early nineteenth century, is useless until they build her a fully working kitchen with running water. I'm guessing the joke here didn't age so well but I find it easier to swallow than Roberta (Janet Munro), the girl who'd been posing as a cabin boy on another ship that Fritz and Ernst see the last remaining crew of on the other side of the island. There, the pirates, led by Kuala (Sessue Hayakawa), are arguing over the prisoners or the loot. Even living as a boy for presumably months if not years can't prevent Roberta from crying and falling on her face before very long when they attempt to run away. Fortunately, Ernst discovers Roberta is a girl when he removes the scarf from her hair, which is cut short, she explains, to look like a boy's. But looking at it indicates to Ernst she's a girl. I'm guessing this was edited down from an accidental breast grope like in Seven Samurai but then, not having any idea how to make the scene work, they just left the blank spot. Because they just didn't care.
When the pirates discover their cabin boy captive is left marooned on the island with a stranded Swiss family, they launch a full on attack to recover her. This is because . . . well, there's no apparent reason. Maybe they want to punish the cabin boy in some traditional pirate fashion, like marooning her on an island.
Much of the movie involves tiresome teenage testosterone competitions between Ernst and Fritz over Roberta's affections. I would probably root for the pirates to kill them if my respect for the pirates' motives weren't so low.
I did like seeing Roberta ride the Zebra in a pink dress and bonnet.