The information that Cuckoo7 gave was spot on! Meeting location, price, lunch, travel time, etc!!!
As far as seniors being able to handle it...another group that was doing the walk to the beginning of the cave, had a lady (I swear) she had to of been in her 80's and she was handling it fine. The guides are great about taking the time that people need and most of the walk is just on flat ground.
I loved that with a 3rd party excursion, you actually float further than the excursion offered on the cruise ships, you get lunch AND the price is cheap (it is still only $50).