Awesome! People don't give the little dudes and dudettes enough credit. I've found that they have the energy to tackle almost anything the adults can do as long as they think it's fun. Congrats on making it to the top, but also doing it with a smile on your faces.
Take him to Langley next. It's comparable to the MT on Whitney, and more scenic IMO. You might also want to try some of the easier mountains by Bishop like Agassiz which have even better views, and he'll be able to see his first glacier?
Yosemite has Lyell, Dana + Gibss, etc...all fine hikes that aren't too dangerous for your son.
