Okay, I heard back from some of the Mt. Airy Parents Network (MAPN) members and here's what I was told -

Flourtown and Beachcombers are not diverse. However, Germantown Cricket Club seems more diverse than other area facilities and may be worth a look, although no one was sure if GCC is offering a summer camp or just their regular swim options. Here's the URL for their website -

http://www.germantowncricket.org/facilities_swim.htm

Best of luck!