First off, welcome to the site.
Second, as JCG has already pointed out, those are all great academic programs, with consistently strong baseball teams. If your son hasn't visited the schools, he should. He'll likely get a gut feel and move on from there.
Third, RJM has repeated an often offered take on Coach Casey. "Difficult" is one of the milder pejoratives I've heard used about Casey (though I would love more specifics on what Casey does that makes him appear to be difficult. The phrase "acquired taste" has also been used on this site for Casey, as well as "old school." )
What's your son's academic interest? Pomona looks like the odd school in this list; Wash U, Emory, and Tufts are similarly sized and, if I understand correctly from what I've read about them, largely focused on pre-professional programs. Pomona, of course, is a shining example of a great liberal arts college, with the advantages of the best weather of the four, and immediate proximity to the other Claremont Colleges. The Pomona/Amherst thread JCG refers to will give you a lot of insight into Pomona's strengths.
And, yes, congrats on those options! Quite a feat. Have the coaches offered to have admissions pre-read your son's transcript and scores?