HAVE HOPE!! :o)
When I read this thread, I knew I had to respond...
Our son has surgery at age 2 for hypospadia (sp?? it's been so long, I probably have that spelled incorrectly). It was a very mild case, and easily repaired surgically, and all is well. However, we were told that his growth "could" be affected, and the goal was to make sure his functions continued normally.
Well, before my son became more modest - we would be bathing him, and become worried that he didn't seem to be growing. Modest is the wrong word to use to describe my son - we actually had to FORCE him to bathe privately - he has no fear of being naked in front of anyone! ha! :) But - when he was age 9, I walked into the bathroom while he was towel drying - made a quick exit (both of us giggling) - and thought he still appeared abnormally small.
Well, our natural exhibitionist is now 13 - and I can promise you - he has ABSOLUTELY MATURED, beyond all expectations (LOL), and.. to be quite honest.. will have NO PROBLEMS in the locker room (if that's where all these male "size issues" begin).
Trust me - at 9 - he was so small, he almost seemed infantile. At 13 - I would say he has surpassed most adult males. :o\
I hope this helps....
It sounds like you are doing fine relative to your discussion with your son. Be sure to discuss your concern with his pediatrician. Some endocrine problems can result in diminished size of penis. Almost always when children are concerned about this they are comparing themselves with siblings or peers and are commenting about what they observe, when in fact there is nothing of a medical nature to be alarmed about.