What does it mean?
Context would help, but it probably means that there is more to understand than it is possible to take in at one time.
Equally, it could mean that the children are so badly behaved that someone can't cope with them. They are too much to handle.
Heard the expression from High School Musical. Troy and Gabriella met in a New Year's party, and in serendipity, compelled to sing together in front of everybody there.
In school, when they were talking about what happened, Troy was whispering not wanting that his friends would know what he did. Then Gabriella quoted, "Is it too much for them to handle?"
So it's closer to my first suggestion - the friends would find the information more than they can deal with.