My SIL lived there for a while and hubs and I visited a few times- always in winter!
October might be too early for Christmas markets but we enjoyed those, and outdoor ice skating (with mulled wine and hot chocolate!)
I'd definitely recommend a boat tour. It helped us get our bearings and it's a nice way to see the city... there are also evening cruises etc so lots of choice depending on your budget. We also hired bikes for a few hours which was a complete riot - it was pissing it down but we had so much fun, they make it easy to cycle everywhere and there are always places to store your bike outside the museums and lots of cafes etc - we are not the most athletic but it was a good laugh!
There are lots of museums if that's your bag - we did Van Gough and Anne Frank, but there are tons, and I'm sure various galleries too. We also went to the cheese museum, and friends visited the sex museum after a few drinks when they last visited - there's something for everyone! 
My favourite thing was just to wander and soak up the atmosphere. Jordaan (hubs refers to "hipster central") is wonderful and the difference between there and the more touristy central areas is huge. It's not a huge city though and the trams and bikes make it easy to get about.
If your intention is to pop into a "coffee shop" while you're there, I'd suggest some research in advance... MIL ended up in one last time she visited, she was shocked 😂 point being some are so nice you wouldn't even suspect. And others basically look like kebab shops... mostly in Centraal where the younger tourists who are there to get smashed are - pretty much! Hubs is straight edge so we never visited or partook but it's a part of the culture so thought I would mention.
We loved it, and always enjoyed the food and drink. I'm sure you'll have a blast whatever you get up to!