We had been worried about reviews saying hiking boots were essential for the canyoning, or that shoes would get ruined. I actually did it in brand new (quite cheap) approach shoes. Both the shoes and I coped fine - no damage to either of us. I would not have been happy in walking sandals though.
The first day - featuring a walk up a canyon - was actually quite hard work. I think the web site refers to getting wet feet but we were soaked head to toe.
You do need to be reasonably fit for this trip but prior experience of any of the activities is not needed. Enthusiasm and the willingness to have a go are much more important. If you are experienced in one or two of them then I think it would still be enjoyable as the locations are so beautiful.
On our rest day we got a boat to the beaches across the bay. The beaches are all private so you pick which takes your fancy by which has the nicest loungers and spend the day buying a few drinks. Lovely.