Ok I am giving no explanation for this one, other than to translate both ways and then whether you are British or American, hopefully you'll know what I am talking about!
An appropriate sentence.....
"We have to decide whether to have a simple procedure done on our son's John Thomas/Peter"
So I would strongly advise the following precautions......
If you are an American and have British acquaintances:
Think long & hard (no pun intended) before you name a son John Thomas.....and naming him Randy John Thomas would be beyond belief - please note!
If you are British and have American acquaintances:
I would suggest you never use the phrase (if you have a son named Peter) "you should have seen what my little Peter did at the match/party/lunch yesterday"!