The best way for your son to get an internship after soph year is to ask around among the older cohorts, make an appointment with the Ross career office, look at career section of websites of companies he likes, contact any connections through you or other adults in his life, and generally “pound the pavement.”
Big 4 diversity summer programs are for under-represented minorities interested in accounting firms. Like this one:
http://kpmgcampus.com/FDL/index.shtml