I have a comment for those who are suggesting sidemount as a recommendation for an aging population. While it has its advantages, it has its disadvantages, too. I know this will sound like heresy, but for most diving, I prefer backmount.
I had an experience that might be instructive.
I started to have arm problems following dive trips--both arms, the right one especially, would get a strange combination of numbness and pain. When I had the same experience after carrying my granddaughter on my shoulders during a long hike, I decided that carrying my doubles on shore at the dive site or on the boat was the problem. I went to a spine specialist, and I was diagnosed with spinal stenosis. They said that was definitely my problem. I got sidemount certified, but it didn't seem to be doing me all that much good. As my problems increased, I went to a different doctor and got a completely different diagnosis. Oh, I had the spinal stenosis all right, but that was not what was causing the problem. My problem was carpal tunnel syndrome in my right wrist, and the pain and numbness were the results of a weekend of carrying gear around. He did a surgical release, and the problem went away completely. It even cured the problem in my left arm--apparently the brain sometimes has trouble identifying the source of pain.
So now I have no problems at all with backmounted doubles, even my anvil-like Worthingtons. IMO, the most important thing you need for the weight of scuba tanks is reasonably strong legs. Keep your legs strong, and your scuba life will be good.