I would guess that the biggest danger for kids in space is that they may get space sick and choke on their own vomit. That and that they may get control of the spaceship and go rocketing around the solar system shooting up planets and asteroids with the ray guns.
Yes true. What made me think of it was a recent F1 accident where the impact was reported to be 51 g. Like you say though, unless there is an accelerometer on the driver or perhaps his seat, we don’t know what forces were transferred to him.
Great multi-part Journal of Improbable Research article on the sled & Murphy’s Law
There is on the internet somewhere a talk on how space travel will affect the very young and the ethics of testing on them, and the consensus seemed to be that it would be some existing astronauts kid who would be taken up, possibly with Mom/Dad with them.
Which sounds like the family trip from hell.
And don’t forget Grandma, too. She’ll be especially helpful once you land on Mars, where the locals remember her from the history books.