We just came back from our cruise on the Valor to Belize and went Cave Tubing. We took my father-in-law (68 yrs. old) with us. The hike getting there took at least 45 minutes and he did very well on this. However it is rough, uneven terrain and there are steps. It is important to note that once in the water Cave Tubing is hard work. You don't just float down stream you have to paddle and work at it. My father-in-law got very tired and ended up walking part way (the water is inches deep in some parts) and not only tough to float on it is tough to walk on. Also, we ended up separated from our group in the dark caves and couldn't find them until the end. We booked this trip through carnival and had a good guide. However, the Cave-Tubing.com groups came through and literally ran over everyone else. It was not fun.
While I'm glad we did the trip I wouldn't do it again and would not necessarily recommend it. There are other things to do in Belize that are more fun.
My 2 cents!