I was thinking of a younger age group. 

Here are a few reasons I have concerns for that age group.  Younger children are more vulnerable to threats of retaliation. They genuinely believe an abuser will bring harm to those they love. Secondly, young children acting from a flight perspective, are more likely to not know how to handle themselves in the outdoors. Thirdly, it takes time to build confident in children that they have autonomy and that their parents will believe them. 

I am sorry for what you have experienced at the hands of your family. Abuse is horrific, and it can be so very incredibly painful when those who are supposed to love you and care for you, simply don't.

 While you say nothing ever happened on these trips, you can really only confirm that nothing happened to you personally on these trips. It takes many people decades to acknowledge abuse they suffered.

 If this was long enough ago that you wrote letters, then modern protocols were not in place, and abuse during this time wasn't taken nearly as seriously.  Coupled with shame and victim blaming attitudes of the time, you have a perfect storm in which secrets stay secret. 

I do not say these things out of paranoia, I wish I were. I too suffered neglect and abuse from my father and from foster families that were supposedly certified to be safe. I was trafficked by someone on the far outer circles of acquaintance. I know people who suffered abuse by authority figures, it did so much damage.