OP here again. Thank you, everyone, for your replies. I now have some ideas ready just in case anyone tries to start an argument at the family get-together this weekend.
As I said in my OP, nobody has criticized me about the 911 call yet. I just wanted to be ready, in case anyone brings up the bill and tells me I should have used my own car. (One of my personal characteristics is that sometimes, if I am criticized unexpectedly, I freeze up. Later on I think of all sorts of things I could have said.) In this particular case, I am sure I did the reasonably prudent thing by calling the ambulance, so I want to be ready -and not freeze up- if any of the relatives fuss at me.
And I hope that our relatives take the high road and do not make a fuss! (I just wanted to be ready if they do.)
Thank you again, all.