I know at least a half a dozen+ kids who decommitted (or were told they no longer fit into the college's plans) before they signed an NLI their senior year. The reasons were various - kid didn't develop and school changed its mind, kid reconsidered the kind of school he wanted to go to, the kid realized he wouldn't get playing time, the kid ran into trouble in HS and the school dropped him, etc. I know another half dozen+ kids who dropped down to JUCO or transferred after freshman year due to lack of playing time or getting cut. In almost all of these cases the kid didn't do his homework, or wasn't honest with himself, before committing.
I point this out because when a kid commits he should feel that this is the school he wants to be at and wants a degree from. He should feel that this is a school he has a legit chance to playing at as a freshman. He should feel a trust and respect for the coaching staff. He should feel like he would fit in at the school. If these boxes are checked I'd strongly consider accepting the offer.
One caveat - an unweighted 3.88 unweighted GPA is pretty strong. Assuming he's taking a healthy load of AP classes and can score reasonably well on the ACT or SAT, he may want to get in front of Ivies this summer at HeadFirst or other camp. He might have a unique opportunity to parlay his baseball talent into a coveted spot at an elite university.