For the OP, some schools are noted for keeping their scholarships intact for 4 years. When your son starts to get offers, I am sure there will be some on this board that can help you through a private message. Keewartson's school was one of the schools that was famous for keeping kids on scholarship. Even if they sat the bench. Even if the coach tried to get them to leave....and the player didn't....the scholarship was there. One player was even offered the same amount in scholarship money form another source just to leave the team (he still wanted to be on the team).
Keewartson's scholarship was spelled out for 4 years, even thought the NLI was for a year. The second year, a different higher amount was offered since a player was drafted and more money was available (YAY for us!). But, in that same letter, the 3rd year offer would be reduced to free up some money for an incoming pitcher (oh ,well). It was basically a wash, but it helped out the coach in money appropriations.
As noted several places above, MOST ALL baseball scholarships are partial, and of the 34-35 on the team, some are getting no money at all. If you hear of someone getting a full ride, they are either lying, don't know much about baseball, or it really is a full ride to probably keep the player from going in the draft after high school. Those are very very few.