Booked this Ketchikan excursion through Holland America with just a wee bit of anxiety -- after all, my wife and I are both 49, not in great shape, and I'm afraid of heights. After the experience, all I can say is, man, I'm glad we followed our gut!
We had an absolute blast! The ONLY complaint I have is that the "expedition" is just too short. The first couple of ziplines are spent trying to get and keep your hands in the right place (which, trust me, isn't too difficult). The next couple are spent watching the rapidly approaching tree you're zipping toward. Unfortunately, that leaves you with only four more ziplines to relax and really just enjoy the ride! (You can't imagine the feeling of ziplining among and beside dozens of bald eagles as they soar above and below you. That and the views of Herring Cove made this activity one that we'll never ever forget!)
Our "expedition" was staffed by young people -- but young people who were incredibly professional and well-trained. They took their jobs seriously and were very sensitive to each individual's comfort/discomfort level. They were patient and encouraging and made what could be a frightening experience both fun and funny. Also, while our group was made up of adults (ranging from mid-20s to late-50s, I believe that anyone from 10 to 80 would enjoy this activity just as much -- age shouldn't be your "determining" factor.
As with practically every "participation-geared" activity, the zipline "expedition" was a bit pricy, but the memories we carried away with us made every dollar an investment rather than an expense.