I work at Liberty University in Lynchburg Virginia. They have a wonderful program called CFAW 4x a year, where you so son can spend 4 days on campus living in a dorm, eating in the cafeteria, and attending special sessions and concerts. The cost is $50.
St Olaf (Minnesota) and Pacific Lutheran (Washington) are laid-back friendly, and known for their outstanding music programs.
Take a look at Concordia Moorhead–it’s just a touch less intense than St. Olaf. Students can participate in as much or as little of the religious life on campus as they wish. A huge number of non-music majors take part in the various ensembles and there is significant financial aid available.
Disclaimer: Concordia faculty spouse, St. Olaf parent, Calvin alum (but for a variety of reasons I don’t recommend it)
Pensacola Christian College
Pensacola, Florida