The most an attorney can charge an injured child in California for representing he or she on a contingency fee in a bodily injury case is 25%.  

NARROW EXCEPTION:  An attorney can petition a judge to award him or her a contingency fee above the 25% but the attorney better be prepared to have good arguments; for example, extraordinary legal work, or other similar reasons.  The judge will make the final call and it is rarely done!

In my San Diego child injury law practice, I have never requested above the 25% contingency fee; I have gone lower than the 25% too.