You should start a weight training regimen; not in lieu of hiking other trails, but as an additional preparation tool. It's a myth that hiking is the best way to prepare for hiking, but that's not to say you shouldn't do it, just that you need to do other things, especially for us older folk. Another myth is if you have an activity, such as hiking that provides much use of your legs than working out with weights is useless or redundant. Totally false. Activities such as hiking is very repetitious activity, meaning that certain muscles/connective tissues are getting a lot of work, but others not so much. Weightlifting will fill in the gaps.
This is a pretty good article on why runners should lift; however, you could just replace the word for runner with hiker and it's just as applicable, actually more so, since up in the area you want to prepare for also incorporates upper body requirements, i.e. rock scrambling.
http://www.nwrunner.com/why-runners-...-need-busting/
One of the biggest advantages to lifting is injury prevention. It will not only give you the strength to do the lifting of the body, it will strengthen you bones and connective tissue.
Also, you can only spend so much time hiking, whereas you lifting can be done virtually anytime, including while watching television. To lift you don't need weights, at least in the beginning.
http://fitness.mercola.com/sites/fit...er-adults.aspx
If all you do is cardio (including walking, AKA, hiking), you will still lose muscle every year as you age, not to mention weakening of connective tissues and bones.
https://www.youtube.com/watch?v=OJoq5c4mPL8