Simplify the following text for a Grade 9 native English-speaking person.
Original: The two teenagers , too young to become Red Cross nurses like their mother and elder sisters , played games of checkers and billiards with the soldiers and tried to uplift their spirits .
Simplified: Because they were too young to become Red Cross nurses like their mother and older sisters , they played checkers and billiards with the soldiers and tried to make them happy instead .