The child/adult numbers were coalesced to reduce confusion. You can also get away with no rescue breaths, not just because of the ick-factor others have mentioned, but because your compression of the chest is also compressing the lungs, providing enough airflow for the needs - and just as importantly, you haven't stopped compressing to deliver the breaths. Similarly, if you don't need to move to deliver the breaths, you don't need to find your correct compression spot on the chest again.