My mom wouldn’t let me go when I was 13, “only kooks would do something like that”. But she had changed her tune a bit by the time my sons were 13. I started taking each of them during the summer before they went to 7th grade. I think it was a pretty positive experience for them. It was the most time that they get spend with their grandmother who continues to ride every year.
My boys had plenty of camping experience under their belts before their first RAGBRAI.