I found the part in the article about priests being the best recruiters very interesting. I had considered the priesthood (before I met my wife) and yet I never had a priest ask me about pursuing it.
I still have hopes that one of my boys will answer the call.
Keep encouraging him without pushing him into it (kids often do the reverse just to make a statement). My Maronite pastor's grandfather was a priest (the pastor chose celibacy) and we have several children in the parish with uncles who serve as priests in other parishes. And then, pray. Ultimately, this is all in God's hands, not ours.