Marina....
I agree with all the responses as well. My son is attending a D3 school in New York (Rochester), thanks in part to TR abd his College Select Showcase. Anyway, you said your son is getting "a modicum of interest" from D1, D2 and D3 schools. Depending on the abilities of your son in baseball, should give you a clue as to which level of collegiate baseball he should play at. I must emphasize "play at"!
Every player wants to play D1 at those "gloried" universities, BUT, do they have the skill level, make-up, size, etc., etc. to compete there. Pick the best school (major/minor, campus environment, location, you know 'the warm-and-fuzzy feeling' he may get while visiting a school, interest by the baseball coach, etc.). This could be a D3 school! As long as he studies what he wants and playes baseball!!!! He may make the D1 or D2, and even the D3 team, but will he play or sit?????? This is an extremely important question.
In my sons situation, he could have easily attended the University of Chicago and Tufts, and played baseball where he was also accepted. But the Tufts coach was "distant" and Chicago just didn't feel right for him. The University of Rochester treated him with respect, as an adult, and followed-up with him on a weekly basis, if not more. They wanted him!! The school has what he wants to study, and has a team where he will most likely play on, I'm sure. He was also accepted to other schools, but felt he might have to wait one or two years to play.
Baseball will not be in his life for ever as a player, but his educational experiences, along with his degree will. It is not an easy time, but I would have him apply to as many schools as possible where he feels he can get the education he wants, hopefully coupled along with baseball.
Best of luck!!!!