ps Maybe he could look into Walden School in Dublin NH for this summer. It is 6 weeks, has interesting classes, composition teachers, renowned visiting composers and musicians (who share meals with students) and every student has a 10-15 minute piece played. There is also hiking and other group activities.
Boston Conservatory has a shorter program that is also really good.
pps At the college level, if he wants to work in CS, he would do internships after junior and senior year so at some point he will have to choose between that and summer programs in music.