The only amateurism issue to worry about is the NCAA, and their rules need to be followed closely.
Go to NCAA Rules page and download the NCAA D1 amnual. Go to page 68, Rule 12.3 and read it carefully. You'll find that you or the player may not enter into a written or verbal agreement with an advisor that would compensate the advisor now or later. Furthermore, don't accept even a free dinner from an agent.
ClevelandDad is correct; there is an implicit understanding that the advisor may benefit later, but you need to keep that implicit. Also, a player sometimes begins a relationship with an advisor, but later realizes that the fit between advisor and player isn't good. It's OK to change advisors at that point (but changing a few days before signing a pro contract would be "dirty pool", although clearly legal, because there was no written or verbal agreement). A player should strive to find an advisor that he also would be happy with as an agent.
As others have said, your player doesn't have any decisions to make right now concerning the draft or pro possibilities. He does need to decide on a college choice. Bear in mind that if he enters a 4 year school, he'll need to have finished his junior year, or have turned 21, or have formally petitioned MLB in order to be eligible for the draft. Some people decide (quite wrongly, in my opinion) to go the JC route in order to preserve the possibility of being drafted earlier.
Regarding "being bitten by the draft bug" or "the fever": You probably can't see it now, but the tone of your posts strongly suggest that you are currently on an emotional high about your son's future. It's very understandable, given all the buzz and attention your son is receiving. But please don't let the possibility that your son may get to play pro ball distract you from making a careful decision on college.