Cruise in nov.to the northern European ports from Southampton

Which ports? A little more detail would be helpful.

Also - why? November is not a good month to visit Northern Europe. Short days, could be sunny, bright and cold or damp, wet and cold.

Just on the face of your "kind of" question. I would not do it. Weather and time not good. But who is the cruise line and what ports of call? By that time of year, most cruise ships have pulled out of that market and headed to the Caribbean.

Our host sells this book which you might find useful. We did on a Baltic cruise a few years ago. I agree that November isn't optimal for weather and daylight, but you should take your opportunities when you have them! And please tell us what ports you'll be stopping at so we know where to focus.

Which ports are you heading for?

If you aren't already a (free) member of Cruise Critic, I suggest you use their 'boards', same as forums. It is all about cruising. You will be able to ask questions about the cruise line, specific ships, there is a section with tips about ports. There will be people who have done the same cruise in a similar time of year. They may be less dismissive than this group. Let's face it; if it is a miserable time of year, the cruise line won't sail that Itinerary. The fact they do, means it is okay.

I agree with Maria, in terms of productive answers.
A northern European cruise will be probably France, Germany, Belgium at that time of year.
Yes the days are short and drawing in, the weather may be a bit unpredictable, but the cities the cruises you go to can be quite magical at that time of year. But the big ships are built to take the weather and are destinations themselves. If it's really windy the ships will adjust their itinerary.
Looking at the Southampton schedule for November it's likely you are on the MSC Euribia to Hamburg, Rotterdam (for Amsterdam), Zeebrugge (for Bruges) and Le Havre (for Paris). Personally I think Paris is a very long day trip from Le Havre, especially with the children, so that is a shorter excursion in the area to me.
First thing I would do is to check the ships shore excursions for each port and see what you fancy.

They could also be doing Norwegian fjords, but I think the OP would mention if that was the case

What sort of things are you looking to do at the different ports? By November many attractions will be shut for the winter.