Share away, Goose! I'd like to read your experiences.
At the beginning of this summer, I had great plans for my 11 y.o. We got up to 9500' Lower Boy Scout on a quick day hike trip, and that went well. But several weeks later, a backpack starting at 7k, and then overnight at 9k went bad. We had to turn around instead of moving on to 11k. Dizzyness and lack of appetite set in. There was no way we could climb higher with those symptoms. We'll try again next summer, but "the kid" is sure altitude sensitive!