Dreams take a lifetime to build and reactions can happen at the blink of an eye. You never want to look back ten years from now and ask yourself "what happened?"
I would sit down with Jr and in the "dad/friend" mode and try to explain that above thought. Remember that he's probably never been in situation where a decision of this magnitude has come forward. Let him know that you will support this decision but will not be responsible for it.
As for the Brothers D1 friend.....Not only do teens have a penchant for over dramatization, an older kids idea of "hard" may look like an unclimbable peak to a 14 year old. If the same conversation was with Jr older brother, the D1 kid would probably say that its hard work but having the time of his life.