Old Dogs

Lately I've been looking at my dogs with a more critical eye than usual. One of them is 13 now, two are twelve and a half years old, and the little one is seven or so. They were all strays, so it's a guess. Initially I was just thinking about how to bring them into condition for our spring-summer-fall walking season, but then I realized I have a certain amount of fear about them at this point in their lives.
In the last 2 years, I lost three of my dogs to cancer.
That's a lot. Of course, I had a lot of dogs. Now I have fewer of them.
What's been on my mind is that I feel like I'm waiting for the hammer to fall, and for one or more of them to fall ill with some dread disease. This is not how I want their advanced years to be, with me counting their days under the worried watchful eye of my anxiety.
I do all these positive things to keep them alive: I feed my dogs a varied raw food diet, and give them a variety of health-maintaining supplements. I walk them outside when the weather permits and try to entertain them inside when it doesn't (even though they just look at me like I'm nuts). I talk to them, play with them, and massage them. And that might have been good enough while they were younger, but now I worry that it's not going to be.
So what to do?
I'm in the process of designing a regular detoxification program for them. Just in the way that some people do periodic cleanses or detox protocols for themselves, maybe this is something we should be doing for our pets. Instead of waiting until pollutants build to an intolerable level, and disease appears, why not try to lighten the load on a regular basis? So here are my goals: it has to be easy to do, consist of high quality herbs and supplements, be palatable, and not cause major detoxification reactions like vomiting or diarrhea.
That's what I'm working on.