One can make a large school small, but cannot make a small school large.
Your son is seeking ways to make the LAC larger through study abroad and taking a year off campus to study at Middlebury’s Monterey institute.
Unlikely that your son will have any dealings with the LAC admissions office as a student so the handwritten note, while charming & welcoming, is somewhat meaningless.
I attended an LAC several decades ago. It was not the right place for me as I was ready to grow well beyond the type of environment that I experienced in prep school. Like your son, I tried to expand the experience by studying abroad as frequently as was permitted (Soviet Union, China, Austria and Eastern Europe). Loved the study abroad experiences, but it didn’t enhance my time spent at the LAC. Too few courses of interest and too few professors.
Attending a major university as an honors student with honors and theme housing should allow your son to experience intimacy as well as challenging growth experiences. This is the best of both worlds.