Vinnie is a little less unhappy, I think. A couple times a day, I go into his room, and he growls a little less. I've also stopped shutting the door, and instead have just been setting a large suitcase in front of it. It lets some air in (Vinnie's room gets warm during the day) and, if any cat actually wanted to get either in or out of the room, they would be able to. So far, no takers among my little family of unathletic cats!
This evening after work, though, I left the suitcase in the hall when I moved it away, and then I went downstairs. Ten minutes later, I heard meowing at the top of the stairs, and there was Vinnie. A few minutes later, he came down to the main level of the house, where I was baking lemon bars. He sniffed around a lot, then started down the stairs to the lower level.
I think this is as far as he got, because Harley was downstairs.
Eventually he went back up to his room. I think I'll leave the door open tonight and see what happens.
Harley's not sure what she thinks of this course of events, but she seems less freaked out about Vinnie than she was about Dolly. And Dolly still doesn't seem to recognize Vinnie, although she lived with him for 7 years!
And, finally, this summer's goslings and ducklings are starting to explore.