You are smart to try to figure this out before he commits. The NESCAC workload is no joke. I am not familiar with Trinity specifically, but S20 is at a NESCAC school and his academic experience has been more intense than his sister who is at a T40 uni and is having a more balanced experience. (She takes 5 classes and he takes 4.)
Within the same school the workload and expectations can vary from one major to the next. Your son my want to speak with Econ majors at Trinity to try to get a sense of the rigor and expectations of that course of study.
FWIW, Bentley is a great school. D20 is friends with a couple of student athletes there who are really happy. (Not football players)
Good luck - sounds like your son has some great opportunities ahead!!