Welcome Autumn Rain!
All mares, you like a challenge!
(I actually love mares.) About blanketing, I think you're doing fine. I have my horses out in daytime, without a shelter but plenty of hay and warm water; they come in every night. I never blanket. I take them only in extreme weather. They have enough hair to protect themselves, never saw one shiver. But your old girl probably needs the extra protection.
We had a few snow falls that don't seem to melt away... winter has arrived!
-12C this morning, more chilly with the wind. We had an exceptionnally warm october, so it's kind of a shock.
Here's a picture of my canadian mare Mistral last week: