I remember seeing this movie as a child - probably when I was 9 or 10 - and loving it. And why wouldn't I? It had tigers and monkeys and shipwrecks and a climactic battle against pirates.
As an adult I find that there is still a lot to like about the film - the genuine sense of warmth between "Father" (John Mills) and "Mother" (Dorothy McGuire) for instance, or the fact that McGuire was actually age-appropriate to be the parent of her movie-sons. It's far too common to cast a 30-year old woman as the mother of a 22 year old.
Also the pirate fight remains very cool.
On the other hand, this is a near 60-year old movie and it has some distinctly 60-year old attitudes. For instance, there's a scene where the two eldest sons have just rescued a cabin boy from the pirates and they joke with one another "wow, I thought that guy back home we called 'sissy' was effeminate, but he has nothing on this guy".
Now it is true that the audience is obviously being tipped a wink here since well ...
If you can overlook the retrograde social attitudes, this is otherwise a fun film - though certainly not a plausible or sensible one - with lots of cheerful adventure.