My 2017 was in a similar situation. The DIII coaches all tried to get him to confirm early, and one in particular was a pretty good match. My son wanted to major in engineering, so that was always his hedge to a full commitment because the DIII's he was looking at did not offer it as an undergraduate degree. The DIII coaches will always try to get a kid to apply Early Decision--that really is their equivalent of getting a written commitment since kids can rarely escape ED. My son was honest and said he was not going to go ED at any school.
We took the approach that finances will play the most important role in his college decision. He got some academic packages that brought the DIII's tuition down closer to in state, but my son was honest with the coaches and said because of finances, he really could not commit until he got the decision letters from the in-state schools (who also offered engineering undergrad degrees). A few of the coaches moved on, but the ones he was really interested in were willing to wait. I suspect that may be the same with your son, particularly if he is a pitcher (my son was both a C and P and some coaches said they were filling their C slots but would wait for him as a P) and has that level of interest from other schools. Fortunately he wound up getting accepted to an instate D2 with engineering and is now pitching for them.