We did several great backpacking hikes in that area when my son was 12, including the Rae Lakes Loop (my all time favorite) and Whitney. 27 years ago now for me. Unfortunately, my son passed away nine years ago. I miss him every day, but so grateful for the memories. He and I did Havasuapi when he was 9 years old too. (Another favorite.). Backpacking and doing hard things together is a great way to raise a strong young man.