The area high school camps are usually very good, inexpensive and fun.
The Wootten sleep away camp in Frostburg, MD is popular for middle-school ballers, affordable and fun. My son and some of his teammates have attended for past 2 years.
Your son can sign up for group training classes and at least practice shooting. I've noticed many very good shooters make the FCYBL teams yet they lack other game skills (defense, passing). The tryouts can be such free-for-alls, many coaches can only focus on shooting skills.