All I can say is if you know that a loved one has failing health, and may pass away at any given time I would hold off on going away. But then again, each individual has to make his/her own decision.
My sister-in-law had been on dialysis for many, many years and because she was so stubborn, strong and wanted to live she was able to withstand 20 years of dialysis, but at the end she lost the battle. We all knew that she was going to die, but the question in everybody's mind was , when?
Anniversarycruisin', if you're not sure if you should go or not, talk to your family, and especially your daughter. Let her know what the situation will be like if something does happen to your father-in-law while you're on vacation. Trust me, it's the worst feeling ever.