I see no harm in your son wanting a pacifier and allowing him to have one. I have two children, my eight year old stopped using a pacifier after first grade, my son who is five uses a pacifier at home. When they are ready they will stop using the pacifier on thier own.
One must however guard against those individuals who frown upon the use of pacifiers and make it a point to shame or ridicule a child which hurts their selfesteem. All too often we hurry our children to independence for our own convenience.
I speak from experience on pacifiers since I have had over time and still do have family & friends who frown on me and my son for the use of a pacifier. However I have yet to see studies that say using a pacifier past socially acceptable notions is detrimental to a child emotionally.
Also, if we look at other cultures children use a pacifier well into older years. On matters specific to our children we must think out of the box. Remember, when they are ready they will stop using the pacifier on thier own. I hope whatever your decision you place your sons needs first.
Oh, I am a 45 yr old mother of two a former engineer and a current real estate investor. And as for my eight year old, she does not miss her paci and if it helps to know she is in a gifted student program at her elementary school. A very smart and well adjusted kid.