redL......The part of you that would like to see your family might feel even sadder if you don't go to see them. It's a short flight and you could ask for some assistance at the airport if you feel the travelling is a bit too much for you. This you would have to ask for at the time of booking. .
I am very sorry you've lost your lovely dog but you were so lucky to have had him/her for 16 years but I'm sorry that you had to watch him decline. My lovely dog was gone in just one week, he was 14 so I do understand what you're feeling.
When Christmas is over you could consider having a rescue dog, there are loads of lovely dogs just waiting for someone like you to come and rescue them. We were lucky that we has 2 dogs so we still have one, he is 12.
I think you should go but only if you really want to and not just to please your son. Bear in mind that the the sooner you book your flight the cheaper it will be as prices rise the nearer you get Christmas.
Another Tired Kicking For The Sick And Disabled By Rishi
NHS U turn on trans terminology