Quoting Captain Spaulding:" This is going to be a post and run, I will be back later. My 2 year old is circumsized, which was not ... [snip!] ... I regret) my sister brought up having to explain why my 2 year olds penis is different than his brothers and fathers penis."
It would be wrong to go against your conscience on a topic for the sake off appearances IMO. Just tell him that everybody's bodies are a little different until he's old enough to understand some basic reasons for you choices......no harm in being honest with him.