I have not made that trip in November. I've been to the Channel Islands twice between May and September. A total of five ferry trips were involved. Two of them were canceled--one of them for three days running. I know one cancellation was weather-related; the three-day business I'm not sure about (it was somewhat rainy in Jersey).
I would caution you to have a back-up plan, because you may not get where you expect to be on schedule. I was lucky not to have to eat the cost of non-refundable hotel rooms when my ferries were canceled, but on my recent trip I had to buy a last-minute airline ticket plus bus tickets from Luton to London and from London to Poole to reach my hotel, which cost a lot more than abandoning the hotel room would have. It was all very annoying and would have been a bigger deal if not part of a very long trip. On a long trip you sort of expect one or two things to go wrong. Tip: The night(s) after the ferry trip(s) are not good times to plan stays at expensive hotels.
I haven't been to Guernsey recently but did enjoy it on my much earlier trip. The islands are attractive, and they have an interesting WWII history. The weather's typically better than in England, but I haven't researched conditions in November.
Given my experience with cancellations (which I realize are statistically anomalous), I wouldn't plan a short visit to the islands in the off-season. However, a day-trip carries less disruption risk, since you and the ferry company should have a pretty good idea of the weather forecast before you set foot on the first ship. On the other hand, there's a lot more to see than you can manage on a day trip.
We have a poster here who lives on Guernsey. I hope she notices this thread and responds soon.