I understand your fears and concern for your child. I don't know what your child's platelet count is and yes all avenues need to be investigated because it is often an indicator of disease.
Yet my healthy husband of 54 years who is now age 76 has had low platelet counts for at least 50 years that we are aware of. His run about 80,000 but has been as low as 60,000 that we are aware of . He was an Air Force pilot, Airline pilot and is leading an active lifestyle. What the doctors say is that his low count is normal for him. He was a redhead, now gray, with thin skin, so he cuts easily but clots about as normally as anyone else.