Where should we spend a few extra days?

Really depends on where you want to go or have been. Certainly could work you way to Paris and come home from Paris. Or swing into Germany. And you could easily spend extra time in and around Amsterdam. There is a lot to see in that area.

You can literally go anywhere from Paris and London to some other place in the Netherlands. Without knowing what your interests are and what places you will already have seen during your cruise, it’s impossible to answer your question.

Check out Ghent, Antwerp, Brussel. If your into World War I history the town of Ypres in Beligum has a fantastic WW1 Museum. Trains are easy to get to each city but not sure about Ypres. We had a car for that journey.

Three-plus hours by train to Paris, then fly home from there. That's what I would do, but you have many choices. Good problem to have.

Bruges is not that convenient to Amsterdam, so I'd visit Ghent and Antwerp from Brugges as daytrips, rather than backtracking to fly home from BRU.

I'd consider Cologne-Duesseldorf, with a 2-segment flight home. I think there finally is a Eurostar train from Amsterdam to London, otherwise a tedious trip.

Are you going to Keukenhof?

(You didn't fill out your home city in your newsboard profile, which helps with transportation questions.)

Thanks for everyone’s thoughts so far. I see I left it too open ended. Not Paris or London, we’ve spent time there before. Our home airport is San Francisco. I’m probably more interested in smaller charming towns than big cities. Flying home from either Paris or Amsterdam probably makes the most sense. We’ve had good luck with European trains (in Switzerland) but a driver and/or small group tour would also work. Our timing is flexible. Really appreciate the input. It is a good problem to have!

And yes, our cruise goes to Keukenhof.

If you are considering going to Germany, that's very doable from Amsterdam. Depending on the departure time, you have direct connections to Düsseldorf and Cologne. There is also Münster/Westf, another direct connection. These cities have radius of 2.5 hours or less. With 4-5 days you have lots of choices in North Germany.