That is true for adults as well. When I did a first aid course the instructor said something like 30-40% of people who receive CPR will have fractured ribs as you need to put a lot of pressure on the chest to do it properly.

"If you haven't heard a crack you are not pumping hard enough" was the rule he went by although they are mostly talking about the sternum but if you hear/feel a rib crack you don't stop. You keep on pumping until a paramedic arrives if you can. A few minutes doing CPR on someone is exhausting. I did 5 minutes on the dummy and after I felt like I was going to pass out.

Thankfully I've never had to use it.