I was trying to think of some less expensive alternatives, but he's a grade too young for the ones that come to mind. For instance, the University of WY seems to have really good funding and has a lot of middle school and high school summer camps that are quite inexpensive. My younger one really enjoyed the totally free astronomy camp she did there last summer, but you have to be entering at least 6th grade for that one or the other one they have for middle schoolers.
If you're in the Colorado area and on Facebook, you might want to join the Denver Mensa Young Mensans FB page (https://www.facebook.com/#!/groups/113887191983766/) b/c a lot of us post opportunities we find for summer and school year academic programs for gifted kids. A number of us have HG kids, too :-).
I don't want to totally turn you away from CBK's summer programs, though, b/c it has been quite a few years since my dd attended and I can't be sure what they look like now. My kids didn't do WATS this year, either. The one thing that I do like about CBK vs. something like UNC's Summer Enrichment Program is that CBK at least requires test scores for admission so you have some idea that the other kids are actually likely gifted. What I'm less sure on is that the other kids are likely HG+ b/c the entrance requirements aren't so high as to indicate that.
