If you are a trousers person, you may feel uncomfortable in a dress which could require you to wear heels too.
However, that coat is lovely and you could wear boots if you wanted to.
I did go to a winter wedding where the bride wore a long cream dress covered by a cream velvet cloak with a large hood; it did look beautiful and unusual, but she was a bit younger (50s) and carried it off well.
Recommendations please, for a stopover on the way to Loch Tay