What worked for my parents is that we have access to some of the best cancer doctors in the world. It really is "worth it" to drive an extra hour or two to consult with a leading oncologist; even if the answer is just "I'll advise the doctor close to your home."
Fortunately, the timing worked out that one parent cared for the other. My wife and I had two babies during the process, so we weren't able to live with my parents, or "commute" them to chemo. We did tell my parents that, if they were going to undergo treatment simultaneously, that we'd need them to live with us so we could take care of them and our children.
What helped is that my parents are naturally active people. They just accepted that they will have tired days, and slowed down a bit. Our biggest worry was that they were both undergoing treatment during summer 2020, and often weren't as careful as we were. The lockdown helped, because we only saw each other on good days.
But, here's the good news: Modern cancer treatment is a miracle. If this happened 20 years ago, I don't think either of my parents would have survived.
Anyway, if you're read this far, all I can say is: Try not to think about it too often. Reframe cancer in your head as a chronic disease, and make an effort to spend quality time with your loved ones. I very rarely tell people I know about my parents' cancer, and this is the first time I've ever posted about it online.