My husband and son did this last july and they loved it. You are up high don't get me wrong but they never felt in danger. One of the families that was travelling with us did the zipline and she is afraid of heights and afterwards she said it was exciting and fun. They had two guides with them and everything was explained to them in detail.
They thought it was exhilarating and quite safe. They had helmets, heavy duty gloves and all the equipment needed for a safe "zip".
I did not do it and I wish I had