The saying that the younger a child gets it the milder it will be is a lie!!! When Aydan first started school at 4 he caught it within the 1st few months. He got it pretty bad and poor little thing used to itch all the time. He was quite happy for us to put calamine lotion on it though even though this was really cold because we could explain to him that it took the itch out.
A couple of weeks later my younger son Lucas got it (he was 2 at the time) and he was covered! Seriously I dont think there was apart of him that didnt have a spot. He spent the whole week crying and trying to rub up on anything just to scratch! To make matters worse he screamed at having the lotion, he wasnt old enough to understand that it was in his best interest! It was honestly a horrible experience!!
I think 4-6 is the best age for them to get it although there is no way of getting this to happen!! Just hope that if your little boy gets it he only gets it mildly! but this then means there is more chance of him getting it again!
Dont think there is a problem with Adults getting chicken pox. The problem is Adults can catch shingles from children with chicken pox, if they have never have chicken pox themselves! (does that make sense??) Shingles is PAINFUL!!!! believe me!!!