This is such a great question. I think Laura V. (Davidson affiliated) may have blogged the question recently, so you might want to go to her Gifted Exchange blog, too.
My spouse raved about a past Nikon photography class, but, of course those were the old days of photography, before digital. But, a huge emphasis on light / dark almost like a cinematography class for a black and white feature.
We always have continuity of activities based on what we love and are gifted at innately. We are specifically role modeling a family environment, but explain that was our choice and our child is free to just be.
If there is some hole in the education (and you re trying to be as well rounded as possible or maybe give exposure to many areas in case that exposure ignites a currently unknown interest), then try to get as close to that area or topic as possible because the best exposure will be very appealing. A watered-down, not so great experience might not be anywhere in the ballpark of meeting the sensitivities of a gifted child. So, if your child loves insects, it is definitely worth it to go to the museums for natural history. The child will love it there if they have an exhibit on insects.
Online programing is fantastic especially if you are in a very hot geographic area at the time and want the children out of the sun for part of the day.
Since you have a gifted reader, we can recommend going to the libraries everywhere you travel. Some of the universities in the areas where you travel are open in the summertime with access maybe to their museum collections. Gifted kids love that!
At this point I think what I might be stating is that summer is a great time to be yourself without having to worry about 'looking cool' in front of any / all peers. It can be a huge relief to the children to just be themselves.
Also, gifted kids are constantly learning anyway. If you take a nature hike, you might not even get that far, because the child stops every ten feet to observe. That's normal for a gifted child, but you may not be able to do that with a group that wants to get to the top of the hike, while the gifted child wants to spend time examining an ant.
Whatever has worked successfully for your family in the past that you continue each year can be such a happy tradition and that will resound positively with the gifted person, which is such a wonderful feeling. Say something as simple as making, heating and eating S'mores to a gifted person is this rich experience of the senses and they will never forget those memories or you. That's great for summertime. Happy summer (in advance)!
