I think this whole topic is really interesting. I am just starting out with summer programs for my second son, but I have learned alot about my elder son's individual preferences in the past 5 years!
My elder PG son (age 10) has a number of very intense interests but overall I would say he likes to "gorge" sequentially at the buffet of life. He eats up a topic then is on to the next. I saw that from infancy but it always takes this mom a bit of time to translate my observations into good actions. Anyway, we have tried full and half day "interest based" summer classes with my PG boy and guess what? He prefers to have a buffet over the summer! That seems to be his general preference whether he is in traditional school or homeschool so I don't think it is a structural issue. I think it may be play based. If he is going to be with age peers he would rather be at a Camp in which he does sports and does interests in which he DOES not excel. In the interest based classes, I think he learned early that he did not find peers and that made him feel more alone.
We did try some gifted programs for him (not the really high end $ stuff) when he was younger but he came back right away and told us that the kids there were being forced to attend and none had a burning curiosity that he had.We tried drama camp and he felt that the kids were just very immature (I saw them, they were)so the instructors could not get much done.
Anyway, my point...what was it? Of course, it was that it has helped me to start having "the conversation" about the summer with my son every winter (say, Feb, when it is cold and we really need to focus on a good season). What do you see yourself doing, etc? He starts to focus, we start exploring the options, etc.We have done this since he was about 7 and it has been extremely helpful. I don't know if other boys and girls have such a crystallized view of "what I want to do" at a young age, but I have found that my kids do and just need to be heard. Next summer may be the first summer for a long time that I am not around all summer for my kids so we will have to work harder at that one but I like knowing that they are onboard.