I would sit down and make a plan. Taking my time with it. There's no rush and you can change it whenever you want. That might relieve some of your "what if" fear. Once you make a plan, let your son know what your plan is. He might have some input.
I agree with the others about the Health Care Power of Attorney for both of you naming the other as the person to make health care decisions in case you can't. I would also suggest you each do a Durable Power of Attorney naming the other person so they can make financial and care decisions, as well. I needed the Durable Power of Attorney to admit my Mother into a nursing home so I could sign the paperwork since she could not.