We have done this excursion twice, most recently last week, lol. It really seems to be one of the best excursions Carnival offers.
There are options to skip a couple of the activities and walk around, I would imagine rappelling would be one you could skip.....however, it really is easy, the guides are actually controlling how quickly you go down, and you dont have to do much.
It's definitely an active excursion. I'm 46 and not in the greatest shape and had a recent foot injury, but all the guides were super helpful and got me through everything with no issues. I would just go for it and enjoy!!!