The concept of traveling with older parents with poor health calls for one decision after another on your part. I feel your pain.
First, it helps if you have a plan in advance of what are the events that would cause you to cancel a trip. Can a sibling accept responsibility for a parent for the two weeks you would be gone? Could you deal with waiting to return to the US if a parent died or would you feel it important to stop your trip right away? These are things to think through.
I have used the travel insurance that comes with my credit card and not purchased additional coverage. I read through the terms and conditions carefully so I knew what was covered and what was not. Mine would cover cancelling for immediate family health issue or death.
My siblings and I have all approached this differently. My sister felt strongly that she could not really travel while my father might need her. My brother felt strongly that he needed to keep living his life and not put everything on hold for the indefinite future. I was somewhere in the middle. I planned and went on trips, but I made sure that my siblings would be covering my father's needs while I was gone. All of these responses are perfectly acceptable. You just have to know what you feel comfortable with.
Sadly, it is not longer an issue as we just lost our last parent. My brother ended up cutting a trip a little short to make sure he was home and had a chance to say "good bye." I certainly don't regret any of the time I took making sure to visit my Dad and that his needs were met. I also don't regret going on my trips either. He loved to look at the pictures and talk about them afterwards.
I suppose what I am trying to say is that this is a difficult issue and only you can decide the approach that will work for you.